I think it's because that, since boys watch MLP just like girls, I guess they want someone, how you say, "boyish". She is also cute to me too. I think her personality gets me(as she makes 2nd place with Fluttershy(who I like just as much).) Imo, the thing that also gets them might be her mane. Discluding Rainbow and Pinkie, it took me forever to memorize all of their names. Rainbow and Pinkie Pie were kinda easy because of their... color scheme. Rainbow also is what, some may call, "cool". You know as well as I do that there are many RD memes out there. So, tbh, I think that sums it up.