Depends on the culture too. Some of those "not sharing" those feelings belong to cultures that are OK with putting your parents there instead of taking care of them -- and think it's "for the better". Others wouldn't (statistically) let that happen, even if they have "busy lives" themselves.
(Another alternative of course popular in some cultures is to let them toil away even at 70 or more, and have them live alone and "independent", with the token visit).
(Another alternative of course popular in some cultures is to let them toil away even at 70 or more, and have them live alone and "independent", with the token visit).