Just want to chime in that I totally agree with Sound on Rosario Vampire, Kurumu should be the main love interest and I'm soooo eager for the new Kurumu figure coming out.
On topic, I'd have to say they got that trope for the guys in anime from real life. So I have read anyway, that guys AND girls are just extremely shy over there (in Japan), right? C'est la vie. I'm not one to talk...32, single, and likely staying that way for a loooooong time.