i am a guy that never puts much stock in what I wear if it has no holes in it I will wear it, but I have noticed that other guys that wear up to date fashions have woman all over them(I have some one)but I know a few single guys like me that could care less about cloths and they can not find a date at all
For me it's not so much about a guy being 'in fashion' - but about a guy looking good. He doesn't need to wear the newest trends or whatever - but when a guy dresses well, and takes care of his appearance to a certain degree, then yeah - it's nice.
It's not massively important to me - I've dated guys who couldn't care less what they put on each day. But it's nice sometimes. If a guy dresses well, it makes him more attractive usually; and seen as we have very little else to base our first impressions on, so a guy who takes care in his appearance and the way he dresses is probably just a little better off in those stakes than one who doesn't.
Most women look at men first to assess how much money they have, and being shallow, they tend to assume that a guy who spends money on fashion must have it in the bank..not always true, but generally yes, of course...
So sure, guys who follow fashion are going to get more attention from most women.