If governments ban crypto then they will without fail ban cash as well.
Edit: For additional context, I live in a country where fees and transactions related to government and regulated services (including telecom) are required by law to use our national payment system exclusively, and it is hell for people who fall through the cracks (e.g. problems national ID that blocks payment systems). I've seen first-hand on multiple occasions people standing outside government buildings begging others to pay their fees in exchange for cash so that they can get unblocked from the payment system.
Whether through malice or incompetence, human institutions can never and will never be perfect. Cash and cash-like systems (inc. crypto) must remain or a lot of innocent people will get hurt, even if it enables criminals.