I guess It depends on the airport, just flown two days ago from BDO and KUL. From BDO they couldn't care less about my cabin luggage, not weighted, probably they would only notice if excessively bigger than standard. At KLIA2 after check in area, before entering to immigration and boarding area there is an agent that weight each trolley/case, 8 and 9 kg were admitted, not sure which is the tolerance limit, but I guess if you achieve 10 kg you will be redirected back to check in. I didn't see any device to check the size, thus estimation will be done visually. Hand bags and common size backpacks not checked.

As mentioned by others different airports may have different policies.