I don't think that is it.

Most airlines (ie: not Southwest) charge to check bags. This causes people like me to carry on bags that are carry-on legal and which get checked on airlines that allow free checked bags.

For example, when on the return leg of a trip, I'll be happy to gate check my rollaboard for free, since it is likely full of nothing but dirty clothes.

I find it amazing that the airlines basically force you to carry that bag aboard and take up the bin space when you have no intention of accessing anything in it for the entire flight.... you are only carrying it on to avoid their bag check fee.... and then since you took up the bin space, it runs out and others are forced to gate check stuff that didn't want gate check.

Letting me gate check it for free means that I don't have to lug around my dirty laundry... and to then give me priority boarding for free as well... shows just how screwed up that checked-bag-fee policy is...