No bank pretends to be fully backed and simultaneously not FDIC insured when in reality 1/2 their assets (before they fired up their printer) are locked up in various jurisdictions because they were laundering money for the cartels. Even HSBC was only laundering a tiny, teensy smidge ($881M total out of $871B in assets, 0.09%) and that was the worst scandal in recent memory.

"Some reason."

Could be, and now I'm just spitballing here, but it could be the use of government backed currencies, the heavy degree of government oversight and regulation, and the federally insured deposits.

You should really, really look at how a bank actually works. You're in for a big surprise!

Barring that you should look at Lawler's article on tether: https://kevinlawler.com/stablecoins

He offers forward contracts if you think he's wrong. He's good for it.