Because there isn't significant money in marketing clothing and cosmetics to men. Men generally buy what they need to maintain a basic standard of hygiene/cleanliness, then move on.

Women have an entire industry dedicated to churning out clothing and beauty products for them to spend money on. Women are generally more likely to be willing to spend far above and beyond what's actually needed on these products because it's seen as a hobby or interest for them rather than just this super basic, practical thing.

Seems like this is why you see so much marketing done to obese and overweight women as well. It's never really been about body positivity for it's own sake, just about companies doing what they can do make the most money.

TL:DR: Men make much worse targets than women for companies trying to market overpriced clothing and cosmetics.