I welcome it. I'm harassed for the 1kg excess in my bag. If you're not charging others more, I'd like not to be treated like that. Give me a discount then for every kilogram I weigh less by.
I think what they mean is that if their neighbor is allowed to weight 120kg with 8kg of carry-on and they weight 85kg, they might as well be allowed heavier carry-on. Doesn't have to be one on one, and of course the carry-on weight limit is also done for a few other reasons, but that seems to be the idea.
To be fair: Carry-on that is weighty is a safety risk. So is me in a window seat with a person that can barely fit into a single seat in the two seats aisle-side from me.
...the overweight baggage charge is because of health and safety, not plane weight. Anything over 20 kilos is too heavy for a single person to safely handle so they have to get two people to deal with it, which takes more time
You on the other hand aren't being handled by anyone. You're not a health hazard.