I hold a decent chunk of change in stable coins most of which I lend out to earn interest. Sometimes I top up a VISA card with those stables and then buy groceries.

You might reply "you're just using a proxy of USD the original currency, its not new".

That's true my reply to that would be:

Having the USD be on chain allows very efficient lending. For eg. I can use a lending aggregator that is constantly polling many lending sources and moves my money to the best source of yield regularly. How would you do this with traditional banking?

I expect over time for the volatility to smooth out as more of the expectations are realised and we figure out a widely agreed fair price for most cryptos (for many this will be zero).