Size limits make sense because there is no point permitting an item that will not fit in the bin, and more specifically rollaboards that don't fit with the short end towards the opening (i.e. 4 per bin vs. 2 horizontal). For 35 years I have rolled 22" onto planes and not once - in 1000s of flights - has it ever failed to meet this test.

Weight limits are complete BS and 100% money grab. As I noted above my rollaboard routinely falls in the 40lb range (= 20kg) and I never been challenged once. Nor has it ever popped a bin door or caused a bin failure. Modern overhead bins are reinforced and designed to hold a great deal of weight. When properly closed (the job of the FA to inspect before takeoff) they rarely pop even during turbulence.

So no, this "self-rightous" American doesn't own a scale, doesn't plan to purchase one, and won't be factoring the weight limits into my carry-on decision. However if A3 insists on maintaining this "policy" then it will certain factor into future purchasing decisions as there are a dozen carriers who won't force me to check my carry-on. And plenty now that bypass ATH directly to the islands.