You just need to regulate the end points. At some point, someone needs real money instead of robux.

Those are the exchanges I mentioned. But no, if it's widely enough used, it can be an entirely self contained system.

But it’s not widely used, that’s the whole problem.

Say you created a business accepting exclusively cryptocurrencies. You need to ship an item? You need “dirty fiat”. Let’s say you’re only selling NFTs or services, your hosting provider wants paid in real currency. Food? Housing? Utilities? Fiat. Fiat. Fiat.

Unless it’s accepted for the entire supply chain of LIFE, you’re screwed.

Look at bittorrent. While it's impossible to kill it, targeting agregation platforms definitely made the protocol immensely less relevant than it was 20 years ago.

BitTorrent made itself less relevant by relying on end to end networking and symmetrical links, neither of which panned out.

Such as? The Pirate Bay still exists as do thousands of other websites listing torrents.

BitTorrent traffic went down as streaming services increased.

Seems like a mix of port blocks and criminal penalties, while not killing cryptocurrency, would greatly hinder its overall utility and thus any associated fiscal value.