One is expecting to hold dollars in a secure decentralized way, but when we talk about those full-backed assets, in reality there is not much difference from the risk of having one's money in the bank.
There is actually a disadvantage, since in this case, one (as final user) does not have a say on what bank to trust.
On the increase of volume, besides increasing from people trying to swap their tokens for other reliable coins on Uniswap, the volume could be also be due to people trying to pocket a buck, speculating on the value of USDC and arbitrage.
I believe we also need to analyze how a government-backed digital money might affect the financial sector. People might store and transact with their money online, reducing the necessity for traditional institutions. This might cause a disturbance in the banking system, and possibly even the abolition of banks as we know them. It is feasible that the government may become the exclusive supplier of financial services, with consumers no longer needing to go through a bank to get their money. As a result, improved knowledge may lead to increased interest in non-government-backed cryptocurrencies such as Bitcoin, among others.