I can't remember the last time I let an airline weigh or measure my carry on. They only weigh your carry on at check in counters. If I have no suitcase, I skip the counter altogether and if I have a suitcase to check in, I leave my carry on with someone or on the side while I check in and that way they never weigh it.
The closest I got to them catching me was when I flew Wizz air intra Europe. The girl by the gate looked suspiciously at my giant carry on which was significantly larger and heavier than allowed and asked incredulously: Did they measure you bag upstairs. I gave her a huge grin and responded enthusiastically: Of course! It didn't fit at first and I stuffed it and stuffed it until it fit!
I've had carry-on weighed by gate.
(I had left carry-on on side by check-in, but the agent noticed it and made me weigh it on scale. Of course, it was overweight. She tried forcing me to pay, but I refused and said I would leave it by a friend in city and wouldn't be taking it. Of course, she knew I was lying, and warned me that I would get stopped by gate and wouldn't be able to bring it onto plane. I said thank you, left, went through security, and then transferred half the stuff from the carry-on into duty free bags. When I got to gate, waiting there was non other than the witch from check-in, salivating over her prey. She grabbed bag from me, weighed it, and was crushed when it was within the weight limit.)