It seems like a lot of it would be due to adverse selection, and that's not something new. Lots of people don't need Swiss bank accounts. What are the characteristics of people who do?

Being Swiss is a good reason to want a Swiss bank account. Rich foreigners might be a little suspicious?

It's somewhat similar to who really needs cryptocurrency, except you don't get the enthusiasts or small accounts, either.

Maybe look at who unmoderated "free speech" forums become popular with. Or who needs to use Tor.