Every clothes maker for women's clothing have their own idea of what size 10 is. From that size, they determine what all the rest of their sizes are. I had a landlord that worked for Pricilla Wedding Gowns here in Boston as a sticher. They were a BIG name in wedding gowns until the designer died and they closed down. She is the one who told me about determining sizes. We had two White House weddings and both brides wore a Pricilla Gown.
Most models are a size 10. Not every model could work for every designer. What is a size 10 for one designer is a size 6 for another. And you expect to win when you go clothes shopping????
If you are talking about runway models, I'm pretty sure hardly any are a size 10. I think anything above 10 or 12 is considered plus size any more in the designer world. I doubt even most print models for regular clothes are a size 10 anymore. Maybe a long, long time ago, but ever since Twiggy, nope.