If you mean to exchange Bitcoin for another pair, it doesn't need banks. You only need banks if you want to convert your Bitcoin to fiats and withdraw to your bank accounts. It is a usual process of withdrawal on CEX, sure it is connected with banks. But if you exchange or swap your Bitcoin on DEX, there is no need for any bank for sure. Well, if there is no bank, we still can convert our Bitcoin to fiats through P2P, Mbitr has told you the example above. And I think, there will be more ways to convert it to fiats in the future. This industry is always growing and developing fast, so don't be pessimistic about the Bitcoin future.