NAFTA (or whatever succeeded it) allows many of those Canadian SWEs to go south for better pay (e.g. Seattle), and a lot of them do. It isn't great situation all around (Vancouver loses talent because they don't want to pay for it).
FWIW the local market is fairly bimodal; there are the FAANG companies and those who keep up with them, and there are some local companies that still pay peanuts. The gap between those two is large.