Yes! Although I live in a reasonably vegetarian-friendly place (a university town), it can still be hard to find decent food when I eat out. I'm not a fan of mushrooms or fake meat, which seem to be the vegetarian options in too many restaurants. And the chain restaurants generally can't tell you what's vegetarian and what's not!
Re: weddings, I live in the South where most reception food consists of wedding cake and non-alcoholic punch.

The last reception I attended that served "real food" had plenty of vegetarian options.
When I'm going to eat at the homes of new friends who don't know I'm vegetarian, I generally say some thing like, "I'm vegetarian so if you don't mind I'll bring my own veggie burger to your bar-b-q" or something like that. I much prefer eating out to eating at other people's houses though so I generally will suggest restaurants that I know have some veggie dishes I like.