People hoping for the next 10x increase, people who want a tax-proof and mobile value store, people who need it for a transaction involving something illegal (e.g. paying off a ransomware operator), people who want it for a regular payment or money transfer.

It's up for anyone's guess how big each of those groups is relative to the others. Believers tend to assume that the last one is big, e.g. the "send money back to the home country" use case.