Why is men's fashion so similar and not as diverse as women's fashion?

I am looking for a gift for my boyfriend, and as I was searching thorugh numerous stores offering men’s clothing, it all looks the same! Specifically, I am looking into getting him a sweater, and they are all the same dull colors (black, gray, navy), and the same design – whether it be argyle, those dams stripes across the chest, among others. I want to buy him something different, but I can’t seem to find it, and also in a reasonable price range ($60 being the top end of what I want to spend). I also don’t want something that is too “feminine” looking, as some different style I feel would look too “metrosexual” on him. Just a stylish guy wtihout being super modern. Any suggestions as to where I could find something different? And why, as women, we have so many different styles of tops, but men’s tops are all pretty simple and not varied?