My camera stuff weighs 5 kgs, my laptop and ipad 4kg, how am I supposed to travel with a 7kg carry on?
Air NZ's 7kg is unrealistic, my 30 yr. old cabin bag, that I have no intention of changing, weighs 4 kg empty, and I take the bare minimum into the cabin, passports, tickets, money, etc. etc. is carried in a voluminous shirt with large packets sold by a travel company for that purpose, so I usually pass the cabin bag Gestapo check - and believe me, they do check, as has been mentioned.
10 kg would probably be more realistic.
Mind you - Air NZ do also print that one is allowed a laptop and "reading material" in addition, so there is room for a bit of a fiddle factor there. ( large tomes hollowed out ? )