For years and years couples can go without. I saw someone on Oprah who did studies showing there are indeed happy sexless couples, and there doesn’t have to be some sort of hidden problem with the relationship causing the sexlessness. Add illness, and that is a whole other set of circumstances that many couples can and do adjust to.
It really has to do with the two people, and no one else’s opinions. I understand the loss as @LuckyGuy put it. Being robbed of sexual intimacy because of illness is a cruel situation. Some people lose interest in sex without illness, but some want to be sexual and illness prevents it. I know people say other things can be done, like fingers and devices, but it simply is not the same, especially when alternate methods are being used because actual sex is difficult. Moreover, when one person cannot have sex, and they are constantly doing for the other, it begins to feel like a huge chore. It can be a depressing chore at that. Even if the sick person enjoys the other having their pleasure, the sick person also has to be there deprived of what they might desperately want too. People understand when infertile people get saddened by seeing their friends have babies; being in a room having to please someone while you can’t, you can’t because life sucks and is unfair; begins to wear on a person. It also makes the ill partner feel inadequate, guilty, and many other emotions.
For me, psychologically, it seems it has been much harder for me (I am the sick one) than my husband. I am more desperate, I miss it more, I feel the loss more intensely. My husband seems to accept it better as life can hand you crappy situations. I think it is different for everyone this type of situation.
I do agree think physical cntact is extremely important, we know it affects blood pressure, happiness, lowers stress, and adults tend to get their physical contact needs fufilled through sex. My husband and I even when I am not feeling well for extended periods still are very physically close. We are always touching, holding hands, spooning, leaning on each other etc. If I didn’t have that I would go insane.