My reasons for having a beard are several fold:
1) I've had several lady friends tell me I look better with the beard than without. That should be enough reason to justify it (unless they are lying to me, then they would be bitches). Alas, I'll continue.
2) I have a baby face and it makes me look older. It's not cool when you're 31 and want to earn/keep professional respect and you look like you're a wet behind the ears college student when cleanly shaven
3) Having a beard keeps the face warmer in the winter, cooler in the summer. The beard doesn't really trap in much heat unless it's massive (and then that's just gross), but it keeps the blistering cold winter wind from hitting the skin and it keeps the hot summer sun from reaching the skin. I shaved my beard off many summers ago because I had a job interview coming up. The job I was working involved me being outside most of the time. It was pretty incredible the difference in how hot I would get with the beard and without. I thought it would be cooler in the summer without it, nope! I got that job I interviewed for, grew it back out after the interview, and I've kept it ever since.
4) I'd have to shave every freaking day to keep looking decent and if I had some night event where I'd want to be clean shaven, I'd have to shave twice. Yeah that might just sound like me being lazy, but I hate shaving to begin with. Any time I can reduce the amount of time spent on something I hate is a win in my book.
5) I save a ton of money (razors, shaving cream) by not doing something I hate. I can not do something I hate while saving time and money? That's a double win!