The stable coins are a great tool for speculators and for arbitrage. And.. that's all. They are not proper coins (they are usually tokens), they are centralized, their value is pegged to a certain value by their issuers, instead of leaving the market decide.
This pegging part comes with certain rules the issuer has to meet (and certify) - usually fiat deposits - which even the most known stable coins didn't properly certify.

So it all comes to the trust in the issuer, in the same way you have to trust your country's central bank for fiat.
I personally don't trust them - neither my central bank, neither the stable coins issuers.