*sigh* Do you not understand the economic principal of volume sales? Marijuana crosses all socio-economic and age groups. I've known many in the over 55 set that smoked weed. Not to mention doctors, lawyers, cops, etc. The designer drugs may fetch a higher price per unit of sale but its the quantity of sales that make marijuana king when it comes to the HA's financial sources. I highly doubt that at least 17% of the population of Canada uses "more fashionable" or "designer" drugs on a daily or near daily basis. Whereas 17% of the Canadian population have admitted to being regular marijuana smokers. Which means the percentage is likely higher. At 17% that's 6 million Canadians who regularly smoke marijuana. I can guarantee you that no other single drug has anywhere near that many regular imbibers in Canada.
Why do you think the HA want it kept illegal? They'd prefer if it was decriminalized for possession but either way, keeping it illegal still ensures they have primary control of the market in Canada.