The fact that you erroneously believe marijuana for recreational use has already been legalized in Canada (it hasn't) probably helps explain why you have little awareness that such legalization has been a political issue since the early 1970s. 

The LeDain Commission in 1972,  the Senate Special Committee on Illegal Drugs in 2002 and the House of Commons Special Committee on the Non-Medical Use of Drugs in 2002 were all formal political processes exploring the need to regulate rather than criminalize the use of marijuana for recreational use. As well, there were two bills introduced to decriminalize marijuana - 2003 (Chrétien) and 2004 (Martin) - only to have the legislation die because parliament was prorogued and the Martin's government fell.  Such processes reflect a shift in social norms regarding such use with the majority of people recognizing the folly of criminalization. 

So your view is your view, but it is not a view informed by political history of the issue.