I have to say I think the point is often entirely missed. I don't think it is so much that people want to see models 'just like them', but more that they want to see attractive, stylish clothes that will fit their body type and they want models with that body type to be advertising the clothes so they can see how it will fit them. Somehow I don't think a normal model modelling a plus-size dress that hangs off of her is going to sell well, nor will a normal model in a petite-size top that's straining to fit her torso, revealing her stomach and has its sleeves stopping closer to the elbows than the wrists. Ill-fitting clothes on models does not tempt me to try anything on, let alone buy something.