The ICO market crashed and trading volume on crypto exchanges keeps dipping lower and lower and lower. Its main use-case has shifted back to currency after a failed bid as a security.
Can you refer me to the source of "crypto exchanges [volume] keeps dipping", please? I'm looking at BTC volume and it's not dipping at all. There was a sharp drop in Jan '17 when Chinese exchanges were forced to close. Other than that volume correlates to the price.
This is a relatively new change though, as in the last year/couple of months. So I wouldn't expect the IRS to have shifted it's treatment. Especially in the context of 2018 taxes.