Why can't guys just approach their crushes?

Anonymous
I know about how guys feel scared of being rejected and how some deal with low self-esteem, but if guys are going to be obvious in having a crush on someone, why can't they just go up to the girls and talk? It frustrates me to see how a guy in college (a friend of mine) would be stalking his crush for the past year and yet never attempted to say a word to her.

Obviously she knows he likes her but she felt like he crossed the lines by invading her space. He has sat near her during lectures, followed her around campus (but brings a friend or two along so it would be less creepy), and makes obvious stares at her. I think she even knows that he talks about her with his friends. So guys, if you do all the trouble of doing these things and it looks like the girl will not make the first move, why can't you just man up and talk to her? It's not like she carries a knife and will stab you for approaching her.
Why can't guys just approach their crushes?
5 Opinion