I don't see how you can legally avoid paying tax over your gains in the US. The only thing I can think of is that you spend your coins instead of cashing out to fiat, which makes sure that tax doesn't apply, but once you have cashed out to fiat there is no escape. If people think they can safely trade on centralized exchanges without being noticed they are delusional. Coinbase has been a warning sign that people should be really careful about how they use exchanges. I seriously wouldn't be surprised to see authorities force exchanges to hand over user information every month in order to see what everyone is doing. If people don't pay their due taxes, authorities will come and take it from them.