I don’t think there should be any huge expectations, but if someone can help out then they should, same as when your parents are elderly, there should be no huge expectations such as moving in with your kids and them being full time carers, but if they can help you out they should.
I also don’t agree that you owe your parents care just because they’re your parents. My MIL didn’t work throughout the majority of my wife’s childhood and when she did it was only a few hours a week, she used any childcare she could find, before school clubs, after school clubs, holiday clubs, neighbours, family, friends, anything to get out of looking after her own kids so she could do what she wanted (usually gym, shopping, beauty treatments etc). Even when she didn’t work she wouldn’t even get up in the morning to take the kids to school, her husband did it before he started work.
She won’t be providing any help with any children we have as she’s now divorced and has to work full time, but I doubt she would offer anyway since she won’t even look after our dog for a day (despite having her own and they get on fine). Why on earth should my wife care for her mother when she’s elderly? Not every parent was loving and doting and would bend over backwards for their kids.
My MIL is selfish and to this day thinks she shouldn’t have to work and should be looked after by someone (as has been the case the vast majority of her adult life). She’s made it clear she expects us to care for her when she’s older, because apparently that’s why she would have done for her mum (I don’t doubt that, but she never got the chance as her mum died young) but I really don’t see why we should when we won’t have the time or the energy (we will both be working full time until we’re in our late 60’s I imagine) and she’s never gone out of her way to help us.