Why are guys so shallow?

There is this new girl in my cl who has huge and she came thi year...so basically me and my bff (vi) are good friends w some of the guys in our cl not dating butjust friends and our cl has always been really tight and close and vi isn't flat chested and neither am I....but ever since this new girl came, all or guy friends have been like obsessing over th new girl even tho they know she's a total botch and I don't want them to be hurt by asking her out for her chest...are these guys getting more shallow and how can I help them?