Mom and dad buy a house for $100,000. When they die it's worth $1,000,000. In Canada, you'd pay gains on the $900,000 difference. In America, you'd pay inheritance tax on the full $1,000,000 (but no capital gains). So in America you're paying tax on a little bit more (I'm of course ignoring the cap gains baseline exception).
But the reason America does it the way it does is because imagine it's not a house but a piece of art that mom and dad bought 50 years ago. No one know how they got it or what they paid for it. How does Canada even reconcile such a thing? How can you pay cap gains on it if you have no idea what it cost and no one is alive to even help you guess?