Regardless of which network, USDT has nothing to do with privacy.
What I meant is that someone who values their privacy and is going to use a service like eXch is unlikely going to interact with USDT regardless of which blockchain it sits on, so USDT on eXch is somehow very 'not-important' IMO, it's not worth the hassle to maintain it even on an existing blockchain like ETH, let alone run a whole new blockchain just for USDT.
People use Tether because its price is fixed which makes it suitable for when they want to exist the market when things get "weird".
I suppose the majority of those people use CEXs; they are faster and a lot cheaper. eXch is a whole different matter, where privacy holds an order of magnitude more value than cost. This means the use case of USDT on any DEX is very weak. I suppose anyone who wants to go from BTC/LTC/XMR to a stablecoin would rather use DAI.