Now, due to social pressures, aged parents are expected to literally give all their wealth to their children so they can buy a house, invest in some get-rich-quick scheme, or pay for childcare/education for grandkids. The pressure is even higher to do so for sons, who have trouble attracting wives if they don't have a house (recall there are less women than men in China).
If, given that donation, their children can buy a home, they move in and behave as live-in childcare for grandkids, while their children work 80-hour weeks to pay off their debts.
Under the guise of filial piety and "being taken care of", the elderly are under high pressure to give both their wealth and autonomy to their adult children. That loss of autonomy matters; if you get sick, you have to rely on your children to navigate through and pay for the healthcare. This may include getting approval to spend money from a son-in-law or daughter-in-law who doesn't much like you (despite their filial obligation to take care of you) and is thinking the money is better spent on more tutoring for the grandkids (in the hyper-competitive education system) or paying down the mortgage.