Canada has some of the strictest requirements for citizenship out there. Simply getting a work visa or similar isn't tough, but I'm willing to be no one here, myself included could pass the citizenship test.
Skill requirements exist, but are pretty paltry relative to the test.
Beyond that, yeah, we don't really want the dregs of your society (i.e. 90% of the IMMA MOVE TO CANADA BECAUSE I CAN'T HANDLE SOMEONE DISAGREEING WITH ME people), thanks. We have enough of our own problems without a bunch of idiots showing up.