The fallacy in this argument is that there's something special in crypto that makes this more likely to happen. There isn't. In fact, you could argue that the enormous activity of scammers in this space actually points to some inherent qualities that might be useful beyond just running ponzi schemes and other scams.
One of these qualities is that scammers are unusually aware and mindful that they might get robbed by people equally untrustworthy on the same platforms that they use. So, the notion that that isn't happening on popular blockchain platforms is useful to them, and others. Tamper proof ledgers are useful for all sorts of things. The history of money is basically increasingly elaborate measures to prevent theft, forgeries, and other abuse. People trying to abuse the system are a constant.
Blockchains and other cryptographic tools are just that: tools. I expect banks to gradually incorporate these tools into what they do. That's already happening. E.g. China rolled out the the e-yuan currency last year. Not a decentralized blockchain but it obviously incorporates some of the technology. Other countries are doing similar things.