One important point is this, just because a wheelie bag is used, it does not imply the luggage is heavier than say, someone with a holdall
Whilst I studied Physics at school, I am no expert but someone at the CAA who investigated the Kegworth crash was! In the case of a trolley bag, the pressure transmitted through one wheel of an empty bag striking someone's head would be equivalent to a soft bag, or grip, weighing about 15 times as much.
That was the reason the CAA quoted 5kgs as the recommended maximum cabin bag weight and no trolley bags! Unfortunately, it was only ever a recommendation and never fully enforceable!
Whoever noticed the "plated weights" of overhead lockers is quite right. Those weights are the absolute maximum the fittings that hold the locker in place are designed to hold, factoring in a bit of leeway for turbulence. Every day, now, these plated weights are being exceeded and, yes, passenger safety is being compromised for the sake of "free enterprise and healthy competition!"
THANK YOU EASYJET FOR COMPROMISING OUR SAFETY - WITHOUT YOU, THE CABIN BAG WEIGHT LIMITS WOULD STILL BE IN PLACE!