Volatility is ameliorated by stablecoins pegged to fiat currencies. Furthermore, the long-term goal is to not need an "interface to the real world", because you will be paid in crypto and you will pay for things in crypto. Even then, who exactly do you mean when you say "the people providing the interface"? I don't need a middle-man to agree to exchange crypto for fiat with someone. You can use one, sure, but it's not required.
Governments have the guns. I doubt that cryptocurrencies will win in the long run, unless they provide hooks for governments to project their power, which includes asset seizure transactions.
As for the people providing the interface, I've since edited my comment. My point used to be that exchanges like coinbase engage in massive market manipulation to aid their own goals, but it's not the only cause for the volatility of cryptocurrencies like bitcoin, so I edited it out.
I suppose there are some blockchains where it is not possible to follow balances between transactions. I'm not sure what would happen with those.
- The Chinese government can get all the main pool/farm owners (all self-doxed) in a room, offer them the choice between being executed or send all blocks their way for central validation. If they choose execution, send government employees to reboot the farms with new code.
- The Taiwanese government can cease the next batch of mining kit as it comes out of TSMC and lol all the way to the (central) bank.
- The US government can tell Coinbase "regulate this thing as told or die". Then all the suits who now own crypto via suit-friendly custodians will in a panic coordinate and fund a 51% attack to save their "investment".
Just a few ideas :-).