If USD works this way, why shouldn’t USDT?
Holding a US dollar is a bet on the US economy, the US government, and the US banking system. Those have their flaws, but there's a lot of built-in checks and balances that keep them reasonably accountable.
The other is that the Fed does all of its currency management very much in the public view. Whereas the USDT management has been somewhere between needlessly opaque and flat-out fraudulent.
2) Tether claimed in the beginning that they had $1 USD in the bank for every 1 Tether issued.
3) Given (2), printing Tether out of thin air that isn't backed by USD deposits is fraud.