Vanity sizing. I think they are also just stocking more of the larger sizes and less of the smaller sizes. Because the size demographics have changed so much in the last few years.  We found her prom dress at a bridal/pageant store and there were a few in her size there. But there were a lot of larger dresses on display.  FWIW, I had to buy a dress for her graduation ceremony from the petite section. I've gone from a med in juniors to a small in petites. Unless I shop the kids section. I'm 5'4" 130 lbs 43 year old woman. I'm not buying dresses from the kids section.