Nice topic OP. The most interest speculations about Bitcoin use case is it decentralizations, but what you need to understand that Bitcoin did not come invoke to replace the fiats rather acts as alternative form to facilitate transactions just like the traditional currencies but of it decentralized mode that users would be custodian to their funds there in Bitcoin.

The essence of stable coin pegged with the decentralized currency does not hold potential of contradicting the decentralization of Bitcoin rather, the associate is to profer price stability since Bitcoin is volatile and the interaction of the stable coins help digital currency users as alternative of exchange for users across the globe to process transactions effectively on the regard that there is still necessity of using the fiats.

That practically is to provide sustainability in the digital finance limiting the need to process your transactions with the banks and also a showoff of the variety that Bitcoin can friendly and convenient be used.
Although the stable coins as mentioned are Centralized values and not compulsory that every Bitcoin users have to use it. It is a choice but generally used to evaluate the values of Bitcoin.