I don't really understand how people (including my better half) get so much stuff in their suitcases. If I packed and then put in another month's worth of stuff in I still wouldn't get to 23kg. I went abroad for a year once and got to about 16 or 17kg.
The other day leaving Queenstown NZ we were called before departure and offered to be put up for another night because of unfavourable winds and tight weight restrictions. So I can see that weight limits aren't arbitrary, and it seems reasonable that if there is an overall limit, people who are prepared to pay can get priority over people like me who would just leave things behind instead. The market at work.
And with cabin baggage, the stuff some people put up there on some airlines is insane. When it gets seriously bumpy (is it just me, or are flights rougher these days?) those doors fly open and stuff goes everywhere. As the doctor on board I don't want to be nursing a passenger with a head injury for several hours over the Pacific...that puts a serious dampener on your flight experience not to mention the patient's...