This is one of those extremely fragile topics that quickly get people very upset on social media- but I am going to sum it up here in two sentences. Luxury brands need to seem to elevate status, so models, location, and clothes all need promote the elevated status. Models who are expensive because of their fame, height, and rare proportions are the most elevated status models you can acquire. There are exceptions to the rule, but the exceptions are all also exceedingly rare- which is what make them valuable. Social status sells luxury brand items, and most designer clothes- even midrange- is about social status.
Emerging designers that want
This is ignoring who designers make their clothes, industry standards, and what people actually react to in marketing. This is just the desire to appeal to people who want the elevated status of wearing designer clothes.
I first noticed this when giving look books to small luxury boutiques- they would judge the models and make assumption about the designer based off the models. They aren’t knocking the models for their aesthetic- they are making judgements about the designer and what the designer was able to afford. It was a signal that the designer wasn’t doing well financially, because if they were then they would be able to get a more expensive looking model.
This attitude is decreased when speaking to specific style tribes, and this attitude change drastically the closer you get to ready to consignment and street wear, as people are more interested in the price of the individual items they are ordering then the aesthetic representations that they are given in look books. These is especially true when talking about white labeling- the boutique knows they will re-shoot the items themselves with models that match their taste.