Well, here's a meaningful purpose by yours truly. I live in Spain and in Argentina. I have to regularly send money to Argentina. International transfers to Argentina are really expensive. Also, in Argentina the currency exchange is being manipulated by the government, like what happens in Venezuela. And all transfers have to be at the exchange rate dictated by the government.

Except for crypto currencies. They operate in a grey market, not forbidden, not approved.

Without bitcoin, I'd have to transfer money at the oficial rate, and I'd have to have another person on the other side filling the endless paperwork they require. With bitcoin (litecoin nowadays, cheaper transactions) it's done in a few hours.