.... In terms of social obligation, that is?
We either go to my parents, or have them here, every year. I am an only child, and I wouldn't have them on their own. Luckily we all get on really well.
Some years we have MIL and FIL too, again not a problem. DH comes from a largish family, so MIL and FIL have other options, which my parents don't. Again this isn't a problem, we don't mind.
One of my Sils, however, insists on the aforementioned Christmas at home with her own little family. Totally up to her. But she's essentially relying on her parents going to her sibling's house, and her in laws going to another of their children's houses for the day. If we all stopped inviting our parents because we wanted a day with just out , then where would they go?
I for one simply couldn't do that to either my inlaws or my own parents. Obviously it's different if your relationship with them is poor, or they have other long standing arrangements. My grandparents, once their children were grown, announced that every Christmas they would either visit relatives in Australia, or the relatives would come here and they'd all have dinner in a hotel. Absolutely fair enough. But my parents and inlaws would be gutted not to have the family Christmas Day. Part of me thinks it would be lovely to have the day at home, every year, with Christmas films and chocolate, pj's on all day, but if we did this it would basically be on the assumption that someone else would be picking up the slack and having the parents every single year, or they'd be on their own. Does that make sense? Again obvious disclaimer that this doesn't apply if your parents are abusive/don't care about Christmas/the other side of the world, I'm talking about families where there is a reasonable expectation that they'll be going round to someone's house on the day