Anybody who is financially dependent on somebody else is vulnerable, whether they are ever in the unfortunate position to feel that vulnerability or not. Typically, it tends to be women.
'Fashion' can mean so many different things to so many different people: fun, money, power, showing belonging to a social group etc etc.
Personally, I don't follow fashion in how I dress, but I know what is going on, trend-wise. I live in jeans and some form of stretchy jersey top off duty, and smart-casual stuff at work. Most of my stuff comes from eBay and local charity shops, so ANY fashion show would waste their time if they were aimed at me. Which they are not, and that is fine.
I am sure that if I lived elsewhere in the world, I'd quite likely dress quite differently, and that is fine too.
But the above comment about not living in a vacuum is very true - and fashion does not exist in isolation either, modest or not.