Yeah, also everybody needs help as they get older, either from medical issues, mobility, whatever. At that point you are forced to rely on someone, unless you just pass suddenly, and if the trust has not been established you end up getting ripped off financially, abused, etc.
I guess you could do it through friendships like Scuba says he does now, but most guys would likely shy away at a certain point of responsibility. One reason being that it's not usually an intense deep intimate relationship if you're heterosexual.