The invention of cryptocurrencies (specifically Bitcoin at least) is not to replace banks, but to replace the way transactions happens. A normal bank transfer involves contracts and processes to make sure everyone that handles the transaction is honest. You basically put your trust on contracts that the transaction will actually go through. Bitcoin replaces this need of trust in the contracts with need of trust in the protocol that can be inspected easier than contracts that are most often private, at least that's the thinking.

> wouldn't you think the banks would be lobbying to have it banned?

There are plenty of examples where the banks in a country no longer accepts transactions from/to cryptocurrency exchanges, Sweden being one example where it's basically impossible to deposit/withdraw SEK/EUR to your bank if they think it has anything to do with cryptocurrencies.

In a ideal world, cryptocurrencies are as protected as normal currencies, and the need for banks are still there as not everyone will run their own node and have custody over their own wallet. Banks adds extra security, something some people want.

Problem becomes when you start thinking that one solution applies for everyone. Cryptocurrencies, just like normal currencies, doesn't work for everyone. People should be free to choose, without being banned left and right for arbitrary reasons. Try getting through banks fraud departments when you make transactions from/to countries like Nigeria, and you'll know what I'm talking about.