Once upon a time, when I only travelled within Europe and APAC, I found the whole cabin baggage restriction thing archaic, controlling and suspected it only as a revenue generating rule.

Now that I've spent some time doing internal flights in the US, I find it a complete relief in regions where they are imposed. Travel is so much less stressful when there is, at least approximately, a space for a bag in arms reach of the seat in which I sit.

NZ do not check on internal legs much, but they do call out those who are obviously flouting it. People are generally fairly well behaved I've noticed and seem to 'get' the rule. sbiddle is right - they will very likely check your bag weight at YVR, especially if it's looking bulky.