I think this depends on comparative income and who does the inviting and chooses the venue and attendees. There isn't a right answer.
My parents have a high disposable income and like expensive but traditional restaurants and can't resist inviting the entire extended family. The bill can easily be £500 and they pay it. I can't easily afford to pay that for a meal, and it doesn't help that for me and my own nuclear family attending those meals is more a duty than a pleasure.
I'd happily pay for just my parents and my own family at a venue of my choice, but that is a rare option - and I have to go and pay on the way back from the loo as if the bill comes to the table my dad will pay.
If we take our own young adult and teen children out we pay of course.
Only one of my children is working full time and she does sometimes say she wants to pay if just she and I go out, and if she says that then I let her and find it really sweet, but I usually try to just pay before she says that.
My teenage son paid for a meal for me once - he had said in advance he wanted to and of course he chose the venue and therefore the budget, but he only has a part time job so I would very much never expect it. It was a one off for a special reason.