It's the consistent enforcement. I've seen a CK required to check.
The biggest issue I see on intl flights is buggies/strollers. They always take up a massive amount space.
It has to be consistent - if it became consistently enforced, there would be no more people deciding that 2" here and 2" there over limit doesn't matter to them - I would agree that pushchairs and similar should be limited to small collapsible ones
I have been taking numerous flights on asian carriers and not once , even in a highly loaded cabin, had an issue with there being space for carry on bags.