Qantas plans to start weighing carry-on bags at the gate. Some airlines have a weight limit on them and Qantas is planning to start enforcing it. For the Australian carrier, that limit is 7 kg or 15.4 lb per bag. They plan to place scales at gates across Australian airports. Enforcement is reportedly occurring on the busiest routes in Australia. This includes the Sydney-Melbourne route, the second busiest air route in the world.
Legacy American air carrier don’t have such limits, but they do have restrictions on the maximum dimension on each side of the bags. But these restrictions aren’t strictly enforced, unless a bag is clearly way over size limits. But with rising costs for checked bags, more people might start carrying more weight on-board and we might see a shift here as well.