Many people have to accept at a very young age that they will eventually serve as full-time caretakers for their family members. Whether it’s a parent who is aging and doesn’t have enough money for retirement, or a sibling who isn’t independent enough mentally to take care of themselves, it’s a big burden to bear.
The duty of caring for another adult is very different than caring for your own child, who will hopefully grow more independent with time and be able to move out and live life on their own. If you’re the caretaker of an adult who presumably won’t become independent, and will likely become less and less independent as time goes on, that’s a lifelong commitment. Sure, some people are more than happy to throw their aging parents into a nursing home or commit challenged family members to be a ward of the state, but most want what’s best for their family, and that’s often staying at home.