I'm a flexitarian, but I'm pretty veggie heavy and have been mostly vegetarian for significant periods of time. I very rarely come across foods with green peppers.
In sandwich shops and some places with tacos and wraps, it's not uncommon to find just one dish that's properly vegetarian - often some mix of peppers, onions, squash, etc. I've always been puzzled by it, considering they tend to be somewhat polarizing vegetables. Something like beans, potatoes, rice, even corn - those things are much more broadly appealing, filling, and probably cheaper, too.
I also find that a lot of places/people don't know much about vegetarian cooking and they seem to think the only way to cure the blandness is to toss in peppers and onions.
Far more bland and full of carbs, too, so they may be more polarizing than you think.