Regarding cultural expectations - in North American culture, things have changed drastically over a few generations when it comes to the lifestyle of the elderly. At the moment, we have government and employer pension plans, coverage of medical care for the elderly, various types of welfare and government support for people below a certain income level, and a variety of housing options for people when they become too old to manage on their own (assisted living facilities, nursing homes, etc).
If you have a society that doesn't have all of those things, having your elderly parents move in with you and supporting them is the default retirement option, with the alternative often being abject poverty when the parents are too old to work any more.
In the parts of Asia I'm most familiar with (Japan, Taiwan) retirement homes exist, but aren't considered a good option, and even if you want to find one, it can be hard. Now mind you, there are an awful lot of grandparents living with their kids and acting as full time babysitters, so the support doesn't come without a cost.
But for parents who are still working, are bad at finances, and are expecting their kids to buy them treats *and* help cover the bills? In that case, it's more like having a petulant college student who blows through their budget and wants you to give them beer money and help cover their rent. In that case, saying no is better for both of you, and giving in just teaches them that they don't have to be responsible.