If vendors everywhere deal in crypto then there is no need to interact with a bank because everyone at that point would be their own bank, responsible for their own financial security.
True but slightly delusional.
The world financial system could collapse tomorrow, Bitcoin could go to $100,000 and you would still be dealing in fiat - or at least some new denomination that wasn't crypto. Even by some miraculous act of God, all prices in all world economies were suddenly to be denominated in Bitcoin (as opposed to, say the IMF's SDR), you still wouldn't be using the blockchain to facilitate trades. You'd be using the same commercial technology layer that's in use right now and you can bet your bottom dollar that WILL be regulated.
Doesn't mean people can't still do blockchain-only trades that are genuinely anonymous though, but it just depends on whether you want to be uniquely stuck in that tiny minority sector of the economy or not.