My question is, which real-world problem is actually solved by crypto? All I know is transferring money over the border gets much easier than pre-bitcoin era.
That's the main legal use-case afaik. If you like travelling to a country that has no banking connection to your country, it might be more convenient to open a bank account or make friends in the target country and move money there via Bitcoin marketplaces. I've seen that plenty of times.
How does that work? You transfer the money in BTC, you exchange that into real money, you open a new bank account, you deposit that money, the bank's anti-money-laundering detection sees a large deposit to a newly open account and triggers an alert, the bank locks you out of the account and asks you for a proof of income/tax payment, you have no explanation of where that money came from legally, they freeze your account and report you to their local revenue services, you're SOL.