stablecoins are useful now, because they are becoming preferred by many due to the speed of transactions and the cheapness of shipping.
"Shipping" Is not a crypto term used in place of "transaction", I guess you are referring to transaction fee here which depending on the chain network you are using, it can be free or extremely low (cheap).
But I hope that sooner or later stablecoins will be more separated from crypto. Because everyone should understand the importance of decentralization and limited emissions, which are inherent in bitcoin. And I consider stablecoins to be an idea that has been profitably "sold" to the masses, but I repeat, I would like this "semi-crypto product" to be maximally separated from the crypto world later.
Irrespective of stablecoins being centralized, they have a true purpose they serve to investors (traders and Bitcoin holders) and the crypto ecosystem at large. It doesn't stop anyone from understanding the importance of decentralization.
For example, those Bitcoin investors who took profits by selling their Bitcoin when the price was still above $120k per BTC benefited from doing so. If they hadn't sold then, the price of Bitcoin would still have dipped, and they would have been sitting in a floating loss waiting for the price to pump again. Instead, they sold their Bitcoin for stablecoins, and now that the price of Bitcoin has fallen, they have the opportunity to use those stablecoins to buy more Bitcoin and increase their holdings.
Assuming I sold 1 BTC last year for $125k (USDT) and held the $125k USDT until last month, then decided to buy Bitcoin again when the price dipped to $58k, I would have bought 2.156 BTC. What does that tell you? It tells you that I was able to preserve both my capital and profits in a stable form, protecting them from Bitcoin's price volatility. I was also able to acquire more Bitcoin than I originally sold during the bull market because I temporarily locked in my profits with stablecoins. This clearly demonstrates the value of stablecoins in relation to Bitcoin and the crypto space.
Have you ever asked yourself why you don't usually see BTC/BTC trading pairs in futures, but instead see BTC/USDT or BTC/USDC? That's because you cannot meaningfully trade Bitcoin against Bitcoin or against another asset that has a similarly high degree of price volatility. You need stablecoins to lock in your profits at a fixed value that won't be significantly affected by the high price swings of the other asset.