The obvious answer is that taverns are a meeting place; it’s where people in the town gather. Thus you can generally find people there, and some of them might want to offer you a job. There is something a little deeper going on, but I couldn’t put my finger on it

There is tension here. If a town exists, it’s pretty good at taking care of itself, but invariably, to make the story epic, defenses have to be rendered sufficiently helpless or corrupt as to make the heroes existence a necessity. That’s the whole point.