USDT is subject to a constant dose of shit and fud, yet it still manages to remain on top of the industry. I'm not saying it's a fantastic addition to this industry, find it shady to a certain degree, but it works and that's what matters.
The volumes on Bitfinex and the fact that those volumes are counted in when people want to get the average price of Bitcoin means that there is some trust in them.
And I am not convinced USDT is so widely used because of "trust". It's so widely used because so many exchanges accept it (and we know that there were many shitcoins accepted by the exchanges in the history).
And people go by convenience too. You don't trust your government, still you use fiat.
With the new "expansion" of the stablecoins, I expect that either USDT handles transparently all the problems (real and not) people talk about or get replaced by other, more trusted stable coins.
With proper 3rd party audit the chance for the company behind the stablecoin to scam people should decrease, no matter it's USDT or a newcomer.