Attraction is massively important in a passionate relationship, which is what some people want, not everyone wants just companionship
As we grow older, attraction and passion begin to take a back seat. There isn't anyone who grows older without looking older and everyone has some sort of health problem. Some health problems are mild, others are more serious but no one gets away without having something. It happens because our bodies age. A partner isn't just for passion, we need to look after each other as well.
Relationships evolve. When you are young attraction and passion are undoubtedly important but as we grow older other things take over and become more of a priority. Even when we have children, other things take over. As a heavily pregnant woman or a woman who has just given birth, passion is unlikely to be a priority. Within a loving relationship a partner will still love you and look after you. They will not reject you because you're feeling and looking like shit after sleepless nights, having a baby belly, massive boobs, etc.
Equally, a loving partner will not reject you because you're ill, ageing, disabled, disfigured etc. At least, that's surely what we all hope for.