The US Government bans a lot of things which are deleterious to society. Online gambling among them.

The purpose is not to eliminate Cryptocurrencies, but to reduce the price of Bitcoin and other PoW coins such that mining (which is a misallocation of our civilization's energy and advanced manufactured goods) becomes significantly less rewarding.

Ethereum at least has a Governing body which is moving it to PoS. Bitcoin does not. Government regulation is the only answer.