Why is there such intense questioning of passengers on flights to US and Canada?

When flying to the US and Canada, the airline usually interviews you very intensely - triple checking your visa and asking you about your plans. The questioning is at times more detailed than what US/Canadian immigration actually asks when you reach your destination. In comparison, flights from North America to Schengen countries are extremely lax - nobody ever asks you any questions or even bothers to verify if you've exceeded the 90/180 rule.

What's the reason behind this? Surely Schengen countries fine carriers for carrying passengers without a proper visa just like their North American counterparts, so why don't airlines check those flights just as strictly?

NB: The above only applies to non-US/Canadian citizens