Many businessmen use USDT for transfers to avoid taxes, for example. The popularity of stable coins is growing, they have low volatility, high speed, low fee, I think that in the end Tether took the first line CMC.
For any kind of business they were using? No! No one will hold USDT just to avoid taxes because it is traceable unlike other decentralized cryptos and can be put on hold in your wallet itself by USDT team.Probably they are using for remittance services to avoid huge fees all over the world and any other crypto will do the same with no issues.