I just wrote a long answer that was deleted. So the edited version:
The generous part of me hosts because I know that I can, and it's gratifying to be in a place where I can provide good food and good company in a nice setting for friends and family. I love seeing people's eyes light up when they bite into something tasty I've prepared, and see friends and relatives who don't see each other often enough get to spend time together.
The narcissist in me feeds of the validation that being a good host provides. I love hearing people compliment my cooking, my baking, my yard, my decor.
The outgoing, extroverted part of me thrives on having others around. I don't care if it's 5 people or 50, an hour's notice or something that takes months to plan, I love it.
The cocky and creative part of me likes having an outlet for creative things like decorating over the top cakes or making a ridiculous recipe and likes the challenge of pulling together things like a backyard party for 50.
We have a very small house - if I had a bigger house, we would eventually host every family holiday. I'm sure that would get old but for now, I would love to have a formal dining room where I could seat 16 people for a formal holiday dinner. We have a great yard, though, so from May to September we host people almost every weekend. Some are planned events (mother's day, father's day, birthdays) and some are impromptu "hey come over for some wine by the fire" affairs. It's a blast, but I have to admit that I'm looking forward to this weekend, which is the first weekend that we've had off since May 6.