I didn't start using AirBnB until 2013, and I used them because they were remarkably polished and made the experience super-easy. They weren't at all a "hair on fire" problem for me.

But I could imagine that at some point in time, there was a group of people who were so desperate for a place to stay that they'd crash on a couple of airbeds at a stranger's place. And that gave those strangers the idea that maybe this was something worth looking into and investing time into perfecting.

The importance of that initial core group of users may be feedback. I've had to give up startup ideas because I launch them and then there is literally nobody who cares. And then with no users, there are no guideposts as to which direction to improve the product in. It's all guesswork, and random ideas don't have a particularly high chance of success.

This may also dovetail with the known advantage that you get from solving your own problem. If it's your own problem, then you know at least one person wants it, and you can use yourself for feedback on improving the product. Then hopefully once it's good enough for you, you can find some other folks that'll find it good enough to try out, and use their feedback to evolve the product.