Outright banning it or taxing the shit out of it have the same effect: buyers go to underground sellers, further risking their health/bypassing legal quality controls.
Source: I'm a weed smoker in Canada. While it is legal here; it's like 80% cheaper to use 'native' dispensaries (shops on native land, run by natives, and thus not subject to federal/provincial taxes). It's been several years since I last used a govt dispensary, and that was mostly because my usual sources were unavailable at the time.
$10-15/gram shatter vs $45-50/gram at a govt dispensary.
At least the taxing option brings in revenue for the govt and keeps people out of jail just for consuming their substance of choice without harming anyone else.