The inch measurements for men don't account for wider hips/bum so it takes a bit of trial and error to figure out what size to buy. Whenever I buy men's trousers I have to buy them 4 or 6 inches bigger than my own waist and then wear a belt to cinch the excess in. It's kind of a hassle and it's definitely not considered a put-together look by most women so the appeal is limited to the less fashion conscious of us.

Probably harder to find pants she likes. Mens clothing tends to be baggy and boxy whereas women's tend to be more form fitting. Even mens skinny jeans could end up looking baggy depending on her size