Why is that? Is it the assumption that everyone who needs an extender is fat? There are some genuinely large humans out there, like weightlifters, wrestlers, pro football players, etc who need to wear extenders. It's not uncommon, and it's not like you need to weigh 300 pounds to need them.

Who would you rather have working the exit row? A 120 pound skinny guy who probably can't lift someone up and over the seats to the door, or a big strong SOB who can pop the door easily and move some people if needed?

Now, if airlines actually had seats where the armrests were actually high enough to rest your arms on, then a lot less people would need extenders. On a lot of my flights, the "male" strap usually comes up right to the armrest. That's a tough place for some people to latch on, with the "female" part of the seatbelt - the latch, needing to come over and rest between the armrest and the person's hip. In a 17" seat, that is tough for even a lot of women with wide hips.

Quite honestly, if the airlines would just put in slightly longer seatbelts - especially the "male" side, the one without the latch - that would generally solve the problem. As is, a new seat cushion that sets up a few inches higher will cause even a non-fat dude to have problems buckling up.