Dollar is not issued on Solana or Ethereum.
Dollar cannot be withdrawn to Metamask or Phantom and then used in the DeFi ecosystem, investing in assets or raising TVLs.
Do you really not understand how huge it is?
Do not worry, just make use of the stable coin on your bank account if you are in United States, you will understand that the stable coin on your account can not be withdrawn to your stable coin addresses. You will have to convert fiat to stable coin on your bank account, convert the stable coin back to the fiat. This is how the banks have been operating, even if they support bitcoin. But at least, bitcoin is an appreciative asset and some people that do not want to buy bitcoin and hold on noncustodial wallet can make use of their bank, although no full control. Unlike United States dollar and stable coins pegged to the dollar to be used in bank. Is it having any use? No. All the questions you asked is about the use of stable coins without the need of the bank which is what stable coins are created for.