Girls and women in general are more interested in fashion because they are bombarded with so many fashion ads. Buy this brand and you’ll be the envy of your friends; it has functional pockets! Men, however, tend to go for fit and comfort. Furthermore, as the previous answer states, women will talk about fashion and have outfits for different occasions. Men, not so much. This stated, a lot of the large name brands - Gucci, Dolce and Gabbana, etc. - are designed by men!
Furthermore, in this age, taking an interest in fashion is often discouraged when it’s a man, unless he’s buying a suit. Men aren’t expected to care about how they look. The entire makeup industry (part of fashion) thrives off women not feeling adequate in their own skin. That dynamic makes women care more.
Sadly, the ages old tradition of women attracting men by appearance rather than by internal qualities such as intelligence is the reason that females may avidly watch what outfits are attracting attention (even though nudity might attract the most). Males are fashion conscious to the extent of some discomfort. For instance, wearing pants so low that underpants show and walking is somewhat impeded.
But this is a desire not to look different from peers, rather than to flaunt a color or design. Women chat about fashion, what they might wear to a certain occasion, what they might buy, and men dont usually have that kind of conversation, so this is a factor.