We travel frequently. Our international size carry on (slightly smaller that NA size) take up 1/3 of the space and weigh anywhere between 7 and 10 KG. Purses, coat, laptop all go on the floor in front of us.
Many of the regional airlines that we travel on outside NA enforce these rules. Not so in NA. Not certain why. On one of our recent trips we got sized and weighted at check in AND again at the departure gate. We do not have a problem with this.
We fly quite a bit. We do not dither about like many. Bag goes up, we sit down, and let others behind us proceed. Too often we are delayed by people with too much, people who are physcially unable to manage even their carry on, or those that like to stand in the aisle open their bags, and get this or that out. All the while holding everyone up. Very selfish.