Depends on your characters and your tone. If your characters are very interested in fashion, they would always notice what people had on. If someone stands out because of their attire, that might matter too -- and even if you don't mention it throughout the book, you might describe your MC's clothing somewhere near the first introduction, if that provides a glimpse of what they're like. Also, some kinds of writing are more lush with their description, in which case every detail can potentially count. (I am thinking of Francesca Lia Block here, who gets every detail down to the shoes in almost every scene of her newest book, but it works for her because she creates such a rich, dreamlike world.)
However, if you are telling a story in a sparer style, and/or featuring characters who don't give a damn about clothes, I'd say skip the description.