The same reason they don't get some of our bikes (Venture, any cruiser with bags and a windshield, TT-R225, XT225, TW200, Vino, Zuma, Vino 125) and the same reason they delayed bikes like the Warrior a year or two from the U.S. introduction- they don't sell in that market, just like the TDM and Seca 2 didn't sell over here when Yamaha did have them in the early 1990's.
blame yourself. Prior to 1997, Yamaha Canada made its own independent importing decisions.
That means we got the RZ up to 1989. We had the Euro spec Yzf600 and yzf1000 (albeit with the dumb "thunderace/cat" monikers. Then Yam USA took over import decisions for Canada and we get the same limited selection as you.