Transacting with it is one thing, withdrawing into fiat is quite another. Let's not pretend that most people holding BTC are holding it to buy goods and services rather than as a speculative vehicle.
Edit: swapping BTC needs a centralized bridge as child commenter notes
Localbitcoins, localmonero... Two of many.
Not true, BTC does have smart contracts. They called it op-code and most people don't use it anymore, but me and my friends built a poker game and we play every Thursday.
The original wallet download also had a poker game, but they decided to take it out after a while to ensure btc wasn't labeled as "Gambling"