Family Responsibility allocations

What prompts the assignment of responsibility? There are always those in the business world who receive promotions because they are proficient in their work, and can be delegated more tasks. But delegation, doesn't always amount to where the work is actually completed.

But what about in families? How is responsibility for taking care of the older generations allocated?
Some generations still hold fast to the belief that the male is the more capable of the genders, and should be put in charge of all tasks. Should gender roles be the deciding factor on who is in charge of the nitty gritty family issues? From who is the trustee on the will, to who takes care of the day to day responsibilities, and medical visits.

Should it be determined by who has the most experience with each particular avenue? Or is it perhaps the favorite relative? When it comes down to it, who is the one who properly takes care of the desires of the older generations within a family?

With my sisters, in regards for our mom when the times come down to it, I know I will probably be the one taking care of mom for the most part. There are several reasons for this, I'm the youngest child, and have had the most one on one time with her. I will probably be the most financially stable. Though my sisters are married, and have good jobs- my career path has the potential to knock theirs out of the ballpark. I am in the financial realm of things career wise. Delegating any remaining money or estate that may be left over should be relatively straight forward for me. All valid reasons, but each of my sisters have reasons and capabilities for why they too could help. My oldest sister being a nurse, her help during doctors visits, and medical attention, would be welcomed.

So why is it that when obviously families can have very capable individuals, do family members end up feeling like they drew the short end of the stick, when they end up being responsible? Why does it sometimes simply come down to those who are actually around, that have always been personally responsible for themselves, that self appoint themselves as care taker when no one else will?

How many middle to low class individuals end up feeling like my mom, forced to give up whatever semblance of the life they could build with their income, to take care of their parents? How many of them have parents that were of a generation that if their children were not the correct gender valued by society, then they were left unaware if they are actually loved, or if they simply are the result of the expectation to have children.

I hope to be able to help my mother before she has need of it, so that looking after her when the time comes never feels like an obligation. But a reason to spend time with someone that I love, and ensure that there is something to look forward to from day to day.