I think this would depend on the situation. Certainly if the parents are in need of 24 hour care, it would be extremely difficult for just one person to care for them 24 hours a day; especially if the person caring for them have a family of their own and they have to work, etc. It also depends on the facility, because if they need nursing care it may be heartless if they did not receive that necessary care. It would also be heartless not to visit them and to show them that you care, however there has to be a balance here, it really depends on the situation.
Also it depends on the amount of funds that we have to cope with the situation. It is quite difficult in these modern times, especially in families where its members are all over the world, to place an ideal on the situation. If the parents are willing to move closer to where their children are, it makes it a lot easier. And if the parents have cultivated a good relationship with the other people around them, that also makes it easier.
So it depends on the situation and the amount of care that is needed. Certainly if there are quite a few siblings then you can work it out between yourself and them to see how you can provide the necessary care for your parents. But when it comes to medical necessities it is very difficult for one person to have to be on call for 24 hours.