There’s supposed to be some utility in crypto. I saw a video with four guys on four different continents and they sent $100 USDC, around the world on the ALGO network in less than two minutes at a cost of $0.40 or $0.10 per peer to peer transaction.
You can’t do that with USD that cheap and $100 in Bitcoin might have been $90 in Bitcoin two minutes later.
That’s one use of stable coins. Another is if some financial/crypto news comes out and you think the crypto market is going to tumble because of the news, you can convert your non-stable coin to stable coin as a safe haven and it costs less than cashing out to USD.