What is the difference between hold money on your bank and hold money in USD? I don't see any valid point to hold huge amount of USD or USDT. If you hold your USDT/USD on exchange then they would locked it for any reason like money laundering and so on. Another issue if they blacklisted your address then probably you will not be able to use your USDT and if company skip then your fund will be ZERO. I am wondering why are you so curious about hold USD/USDT. That's the disadvantage of centralized crypto-currency, crypto-currency shouldn't be centralized at all.