Sometimes they do though... even in Canada!
One of my flights out of Vancouver about 5 years ago before my temporary residency in Costa Rica had completely processed an Air Canada agent asked for my return ticket (return to Canada, that is). I replied that I didn't have one yet, she asked how long I would be away and I said about 5 months or so and would purchase it at a later date. She was NOT going to allow me to board that flight without either a return ticket or a resident card for CR.
I told her I had a temporary resident status that was being processed but hadn't been completed until I went back to pick up the card. She wanted to see any document as proof. I had copies which were in my laptop, so she gave me a desk nearby and told me to find the documents. It took awhile cause I couldn't get onto the network at first, then couldn't find it right away, was getting panicked because I needed to be on the flight and it was getting too close to boarding time, etc. Finally found the documents and she showed her supervisor who accepted it and they let me go but had to get me a cart to get to the gate because I was so late.
I've traveled back and forth ever since June 18, 2013 approx. 4 flights per year most years and I've never been asked before or since for this, but that time she was very serious and not going to let me get onboard, so it CAN happen! :0
