I'm 6", not overweight, and from Europe: seat width and pitch is a big issue for me. Economy seat width is typically an uncomfortable 17-18 inches, and pitch typically a painful 31".

I have to fly long haul in economy with work (who won't pay for anything else), so my choice is either several hours of pain and discomfort, or to pay a large sum to upgrade myself - if the fare is even upgradable. Bring on the regulation!

While the overweight-passenger issue is a real thing, in this case the seat pitch affects people who are taller. 28" (711mm) seat pitch (which includes the thickness of the seat), doesn't leave much room if your femur is longer than that. So all the Dutch and Scandinavian fliers would really suffer on a 4+ hour flight.