You misunderstand. The very reason that this Binance hack is a huge issue is that $5B was concentrated in specific wallets under specific keys.

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.

I'm not so sure.

Centralization (on Binance) made the attack appealing, but decentralization (of crypto broadly) is the only reason it's possible, and centralization (of USDT et al) is the only path to recovery.

Re: the marketplace: we'd want to be able to revoke teacher access too, and sometimes we may need to roll back transactions (Goods not delivered? Wrong goods delivered? Wrong goods purchased?), and then I have to ask... why involve a blockchain at all?

The only compelling real world use case I've seen is helping people navigate hostile governments or dysfunctional economies.

The number of scams perpetrated against traditional bank account holders doesn't seem to support the suggestion that scammers aren't interested in regular person-sized targets.