Anyway, the brain in a jar is basically we don't have a body, we are just brains in jars kind of like the idea in the Matrix movies of which you become aware when you take the red pill. Our senses are delivering a simulation of "some reality" to our perception, the 'I' as some might call it. And there is legal precedent for this, we are not our DNA in that we are created 'equal', it's illegal to discriminate. Technically I think we should be of equal 'value' although without the financial implication. Technically this is called the Mind-Body problem and is a well established problem that is known to philosophy.
Asking men why this happens some have suggested that men (boys) must quickly learn to turn off the urge to get an erection at a very early age and relatively early - because erections are socially embarrassing. It means that the boy has no self control (as an aside, its interesting that if a girl gets raped society wants to know if she was drunk and what she was wearing. This implies in private its acceptable for a boy/man to lose control? I think this is insulting to men/boys because we know men/boys can control themselves).
In polite society it's like our bodies disappear. We don't discuss our body's normal functions. We use bathrooms in private, we never discuss our secretions or excretions in public - they may happen but no one wants to know about it including periods. We project perfect bodies, especially women, well groomed, good looking, young.
The sick are hidden out of sight; men prefer to ignore things going wrong with their bodies, often ignore symptoms until it is too late; and the elderly are usually put into homes where they generally can't be seen. Babies and the young are also kept out of sight from most adult work environments. This may be why breast feeding babies is often considered unacceptable? We don't want to be reminded of the aging process and female body 'ornaments' (breasts) might actually serve useful purposes - it reminds us we are going to die and for most of us we live in this fantasy we will live forever.
Women remind men that men have bodies - because women make men get erections (okay I am generalizing) but men do have to evaluate each woman and give her a rating and then figure out whether they have a shot or not (yes still generalizing). This is very likely one of the reasons why men sometimes resist women in the work force. Women remind men of their bodies of which they'd rather not remember.
Bodies are something we don't want to think about. And this is why the brain in a jar is such an attractive concept to most men - because that's the ideal. There is only the illusion of pain, need, hunger, desire when you are a brain in a jar other. Brains in jars exist in worlds of concepts and abstractions often not connected to any reality.
Eating food has become glamorous and is also disconnected with the idea of actually nourishing human bodies - because nourishment is the last thing in the minds of large corporate food chains and the "food" products they sell.
I think this is why our society is hyper-sexualized, because I think that some men think women are like the icing on the cake. Women are the reward men get when they feel like they have done something worthy. What I mean by icing on the cake is women (are meant to) look good, women are all warm, soft and good to hold, women stroke men's ego, they get affection (aka sex), or comforting (this is often when men seek out prostitutes), women give men the feeling of being connected and needed and give men a dopamine rush.
But I think for some men, women aren't generally considered useful for much else. Being a brain in a jar we stop being animals. And this is probably the appeal of the singularity because it proves we can exist as brains in jars and then live forever and we don't need our body. Hence it makes it easy to anthropomorphize (or rather identify with) computer networks into being brains in jars, rather than tools that perform operations based on our ability to act.
We feel uncomfortable remembering we are very much dependent on our bodies, but animals we are, we give birth like other mammals, we produce milk like other animals, we mate, we produce offspring like other animals which often gets turned into something 'miraculous' by 'christians' so we can distance ourselves from the fact we are nothing but (extremely clever) animals (and I don't mean that in a derogatory sense).
Advertising makes use of this by often placing subtle and sometimes not so subtle sexual messages hidden in their advertising.
But when men really want to get stuff done, what they consider important stuff, they go seek out other men and go off and do it together, like war, build businesses, drink beer and watch ritualized war (aka sports) together. To men, men's stuff is the important stuff.
And if they do anything for women like acknowledge women's existence women should be grateful because women aren't really that important. Women's purpose is pretty much purely for recreation. What women say is kind of trivial to them and yes I am generalizing, I hope. That's why women's studies are not taken seriously, important women in history tend to be ignored, what women do, think and invent is irrelevant, because it's men who feel men do the important stuff.
I think this sets up a problem for men - men very seldom get intimacy from each other, they do not get warm from each other, they don't make each other feel connected, although they may feel they perform useful function in their work, they very likely could be replaced by someone else. (Yes again I am generalizing)
Nevertheless men do need to feel connected, they do need the warmth of a woman and companionship because they are animals despite how much denial they may have over having a body. The warmth of another human being is essential to our well-being. Those statistics on the number of hugs we need a day aside, we need affection, touch and warmth, it is part of being an animal and having a body. The icing on the cake is an essential component of life and it is only thought irrelevant because we are in denial about our bodies.
While we can live with the belief humans are bodiless for the most part, we do need our bodies to develop our brain. Our brain learns how to see after birth, this is not the same as being blind at birth, our brains must learn to recognize and understand what our eyes see after birth. We must learn language, we must learn the relationship between space and languages because I believe it is via our senses that we actually think. Whether we think in words or think visually, our thoughts are expressions of and derived from our sensory input, and for those who are born deaf and blind, they learn via touch. What feels good and bad is salient to how we choose to operate in our lives.
I think men think this function women provide is of no real importance but I think it may account for the high suicide rate of men. Men sometimes think cultivating their relationships with women are irrelevant, that they are enough. As a result women end up not expecting very much from the friendship and seeks the connection she needs else where. This will end up meaning the man will no longer have any connection. This often results in suicide for the man because there is no one who needs or cares about him anymore.
While women do go along with denial about their bodies by pretending they don't get periods or have body hair and being perpetually young, women do acknowledge they have bodies and part of this is taking care of their body because women are supposed to fulfill this function of being icing on the cake. And perhaps this is part of the myth women are their bodies but men live in the fantasy they are brains in jars.