You've got that backwards, exchanges are only used by people with USD or trying to get USD. The Bitcoin ecosystem did just fine before exchanges existed. I was there. We either mined our own coins, or earned them by doing work for people with coins. It was great.

Also recognize the privilege that you were born with that allows you to open a bank account. About a third of the people in this world don't have that luxury. I've used Bitcoin to pay under-served artists and programmers in corners of the world that I had never heard of, and with many of them I never knew where they were located geographically, because it just doesn't matter anymore.