Cash is more often used in money laundering and do you think that cash isn't even used for illegal activities? It's even the most used currency for those methods and this taboo about bitcoin must be changed.
Bitcoin is very much welcome in commercial use and from the perspective of being used illegally, that's changing into the mainstream day by day. It doesn't mean you use bitcoin because you are into illegal activities. You use bitcoin because you know that it's a good investment and a good alternative payment method.
Not only that but cash are mostly experience inflation in these past years, many countries nowadays who now prefer to use digital currencies because of the inflation. Like the country of Venezuela where they experienced hyper inflation that leads to their many citizens to migrate in other countries. I saw a image yesterday where you need to have a lot of cash in order to just buy a whole chicken. Imagine the inflation that they are into, we really need bitcoin because what happened in bitcoin is deflation.