> if some women absolutely can't find something in their size from a specific brand, that makes the brand even more exclusive, like it being "for fit people only"

The elephants in the room from the raw data is it is very clear some brands do not want average middle aged women wearing their products. Anthropology seems to be the most clear about this in that they have a literal gap between their standard and plus-sized ranges that excludes the adult median woman.

Now some brands might do that out of snobishness, but I expect there is a feedback loop here:

1) Young, attractive women want to make fashion choices that signal they are young, attractive women.

2) They buy from fashion lines that don't fit average adult women.

3) Average adult women detect that the fashionable choice is these brands and feel left out, because a fair number of them would also like to be young and attractive again. And a small but significant fraction feel really left out if some clothing brand calls them a size 20 waist / fat / shaped like a rectangle. Clothing brands detect this in their customer studies and respond appropriately.

4) People who just want clothes buy from H&M or wherever and don't write articles about how hard it is to fit clothes.

"Women" isn't really a homogeneous category when it comes to clothing, there is ongoing fierce competition between lots of different sub-groups of the female population to signal lots of different things. Men have it a bit easier because there is basically a 4-quadrant choice between upper & lower class, formal & casual with a lot of intricacy for people who care a lot about what brand of black leather shoe they own. Young girls are closer to men in that they aren't really trying to signal anything at that age, so clothing fits are a lot easier to manage.

> Clothing brands detect this in their customer studies and respond appropriately.

Respond how?

> lots of different sub-groups of the female population to signal lots of different things

Signal what?