My parents help me/my kids out a bit, not just at Christmas, but with things like school uniform, shoes etc. They buy big ticket Christmas and birthday presents for my kids, usually as well as me buying them expensive presents too. This year we've gone halves on some presents, mainly because the kids are asking for more expensive tech stuff as they get older (mobile phones, gaming PC's). When we get together they pay for all of us for things like family days out, meals out etc. We all go camping together in the summer and they pay the camp site fees.
Now they help me out quite a bit with child care, that's probably the most significant thing. They live 300 miles away, but recently bought a 2nd home near to me (put it in my sister's name, helping her get on the property ladder, because she's 40 and would never have done it herself). So now they can come up here more often to spend more time with their grand kids.
For context though - my parents are boomers who both had decent white collar jobs with very generous final salary pensions. They both took VR and early retirement in their early to mid 50's. And they were always very prudent with money (as kids, we never almost never went on foreign holidays, just camping, and they always drove old bangers, we rarely ate out etc). So now they're retired, but with pension/investment income pushing them into higher rate tax brackets - they basically have more money coming in than they know what to do with! Neither of my siblings have kids (and it's looking less likely that they will as they are 40's now), so mine are the only grand kids. So I'm aware that if they had more grand children then their attention would be split.
I can afford to provide for my kids by myself, my parents buy stuff for us just because they can. So the way I see it, they're making up for what I (possibly) missed out on growing up because my parents brought us up quite frugally at that time. We don't strictly need their help, and I don't ask for it, but it's nice to have.