So when someone is planning on inviting you over for dinner and is thoughtful enough to ask, "are you a vegetarian?" you can go "I'm omni-curious." And of course they'll say, "what?" and then you get to spend extra words explaining yourself about how you ate meat once 3 years ago.
Even pretty strict vegans may on rare occasions consume an animal product, like some medicine that happened to have some animal component in it, or something. In Scott Pilgrim, the vegan had three strikes before the vegan police took his vegan powers away.
I was a vegetarian for about a decade until I eventually stopped and became a pescetarian. But like, there was once during my veggie years where I flew across the country to visit my mother on Thanksgiving that I hadn't seen for many years and she's like "I have a big turkey we'll cook today. I don't normally eat turkey on Thanksgiving, it's really expensive, but I got it because you were coming! I hope you like it!" and so I thought, "oh crap, she doesn't know I don't eat meat". So I made an exception and ate a little bit of turkey because it would have gone to waste, it's not like it tasted bad or anything, and it just wasn't worth being a fundamentalist about. You gotta pick your battles, right?
That's an instance where labeling myself more quickly would have been helpful, actually. Labels can be useful.
Or like, I went for a check-up, and the doctor asked me if I was vegetarian and I said "yes", because in many years I had eaten meat like once. I'm not going to ramble on about how "technically that's complicated, because a couple of years ago on Thanksgiving..."
So if someone asks me if I'm hetero, I'll say "yes", not "well its technically complicated, usually I like guys but there was this one girl in freshman year and we kinda...."
I was a vegetarian, and a rather strict one, but not a veggie fundamentalist. And I'm basically heterosexual, but not a hetero fundamentalist!