It really depends on a variety of things. If people are spread out geographically, if they travel for one, they don't for the other. If people are relatively lo

It really depends on a variety of things. If people are spread out geographically, if they travel for one, they don't for the other. If people are relatively local, often one holiday is with one side of the family while the other holiday is the other. After a generation of couples having 2-3 kids and those kids growing up to have 1-2 kids, it makes sense that "extended" families aren't all that extended any more. One of my grandmothers was the oldest of 7, while both my parents were oldest of two, and I'm the oldest of two. Add in our physical distances and it's easy through honest poor scheduling (vs malice) for a grandparent, sibling, etc to be 100% on their own for a holiday.