Почему стареньких людей сдают в дом престарелых?

According to the law - this is possible only if the children are not capable (eg disabled). Then the state takes on the responsibility of caring for their sick parents.
If children are not well off (alcoholics, etc.) or simply do not want to take care of their parents, then such old people will not be accepted into the nursing home, they will not be attached to a social worker.

http://androidmafia.ru/video/Ca04AJN1644
There are various reasons why children send their parents to a nursing home:

1. The accumulated resentment, not understanding, dislike.
2. There is no financial opportunity to buy medicines, to provide proper care.
3. They believe that it will be better for the parents, in America they say they do so and nothing.
4. Mental disorders of the elderly, when their children simply can not cope with the situation (work and therefore can not be near 24 hours a day), a very complex disease and need hospital care.
   I feel sorry for such old people. They should live out their days among relatives, in their native walls, in the usual environment. They haven't handed over their children to the orphanage, so why are they now doing this?But at the same time don't want to judge. Life situations are different. There are cases when it is simply impossible to do otherwise.