bitUSD and bitBTC are centralized solutions. The exchange rate doesn't magically sit at one, they have a fund manager.
There may be some utility there, for the darknet, but when the feds shut down the fund manager it all goes to shit.
Look, cryptocurrency functions very similarly to how Liberty Reserve worked. Liberty Reserve servers stored fund allocations and transfers as cryptographic signatures, and then deleted the records. Feds shut it down because it was centralized and easy to shut down. The market adapted.
I thought NuBits was pegged to the USD via bots, is that the one you're thinking of? Doesn't bitUSD have an entirely separate market based mechanism for attempting to stabilize the value?