This is part of the Canadian border control in my experience; i.e.

- Arrive in Pearson

- go to passport control, scan passport at kiosk, kiosk spits out receipt

- you flash receipt to a border officer at the stairs out of passport control

- go to baggage claim

- get bags

- go to customs

- hand passport with receipt to officer at customs

- welcome to Canada

I haven't had that experience when leaving other countries bound for the US; like GP said, I've had to show my passport to the airline to board, but I believe that's to fulfill the requirement that they made good-faith effort to ensure I'm capable of entering the US.