I do not think they provide anything worthy aside from using on their own platforms. For example using USDC on circle or poloniex makes sense because there are people who can withdraw that directly to their bank accounts, of course it doesn't make any sense to use it if you are living in a country where you can't withdraw the money but if you can cash it out to your bank directly than it definitely is a useful coin.

Aside from helping with that the idea was to keep your cash in fiat while crypto is on a drop and if you wanted to do that on multiple currency exchanges you had to usually withdraw bitcoin to your local website and cash it out which took time and effort and cost you, with the stabletokens it is simple but it is also dangerous because it is not actually backed by dollar but only symbolizes it.