Some smaller people might like the option of paying for a bigger seat for the comfort.
I think bigger seats should be offered, at an increased price. I suggested this in another thread, about a year ago. I suggested planes have some larger seats in the back rows, where, maybe for larger passengers (not just overweight, but some large men I could imagine might appreciate a little extra shoulder room, or a mom with a baby or dad with a baby for that matter). There may be larger passengers out there – or should I say potential passengers – who don’t fly because they are afraid they won’t fit into the seat. Why not accomodate them? If they are willing to pay extra, why not? People pay extra for other services on planes, why not extra for a larger seat?
I am a person who once would have had trouble fitting into the standard plane seat, as I was large, too. I would have gladly paid more for a comfortable seat.