The stolen USDT will likely be returned because Tether can do manual freezes like a traditional financial institution.
Where code is law the funds are just gone.
Like even in your example of the marketplace I don't see the benefits over having a central authority. Who determines who is a student or teacher? Who kicks out bad actors? Who resolves disputed transactions?
A decentralized network of wallets and balances doesn’t present an attractive target for hackers specifically because the payoff per wallet is so small!
It is exactly the centralization you are defending, which is at the root of the problem. In the decentralized case, no one has to determine who is a student or a teacher. If a teacher needs to pass KYC with a marketplace, they do it once, and from then on can permissionlessly receive their small payouts.