Over 40 to 60 percent of USDT are in Tron blockchain. Fast verification and low transaction fee. Life made easier with USDT TRC20.
Solana and Avalanche are blockchains that are at least a lot more lively with a lot more platforms than Tron despite both being quite young. So, yea.
It's not like you're suddenly not able to use USDT on Tron though; it's just that expect all the hype to die because Justin Sun sure is a great marketer.