An interesting primer on Tether, and whether it is a scam: https://www.zerohedge.com/crypto/what-effect-would-tether-be... (Yes, I know it's zerohedge, but this is a decent article) Tether usually has 2-3x the volume of bitcoin in any given day. And no one seems to know anything about how it works. So in my estimation, it probably is a scam...
USD is the real scam. It's not backed by anything either. Tether only exists because nobody else wants to touch the USD and its annoying regulations. I find it hard to care about Tether printing billions when the US government prints trillions. Wish we could have a 100% XMR world without even a single dollar in sight. Won't happen until the end of the petrodollar which won't happen until the end of the US military.
But why are you conflating USD with crypto anyway? USD is a currency that is actually used for purchasing goods and services. Crypto isn't used for anything except speculation. If capital gains is the goal, then yes, the USD won't be of much value to you as it's not particularly volatile.