I think it's certainly fine to be grateful for your parents if you like them. I had pretty ok parents so if they need help as they get older I'll probably help where I can.

I guess I just get a little annoyed that people act like you are supposed to. I didn't choose to be born, and as far as I am aware neither did the other eight billion on this planet. The parents were the ones who brought the kids into the world. The kids are their responsibility, not the other way around.