Crypto indeed doesn't need banks to exist, but the far majority of the people want to see prices increase. In order to do that, money has to be wired to a bank the exchange in question works with.

If you take banks away, there will be way less liquidity coming into crypto, that the prices will keep falling and investors will lose interest. Crypto has only speculation going for itself. Take that away and you're left with a house of cards.

Only when Bitcoin has really grown on people as store of value and they appreciate the decentralized nature of it, then things could be different, but we aren't anywhere near that point yet. Be careful what you wish for.