I think it's more a fear of oneself; a fear installed in us shy/introverted guys by society.
We are raised in a society that we do think condones approaching a girl; that it is pretty much frowned upon. It's cemented in us because we've never see it done during the day and the only time we think it's acceptable is during the night, in a club or a bar.
Which is hell for us guys that loathe bars and clubs.
I know about flirting signals and body language - and yet I'm more often than not incapable of approaching those girls that are giving me the green light to talk to them.
It's infuriating for me. Even earlier today I saw in my college a girl walking past me that just a few days earlier had given me the green light to approach her; and she thought she was going to be approached by me the last time we noticed each other, since she saw that I was picking up her signals left and right - this last time (before today) is when I was walking towards the rubbish bins to throw away my disposable coffee container that I had got in my college's cafeteria, and she was right behind me - following me. I noticed that when I turned around, after throwing the container, and saw her standing right behind me; she saw that I noticed her so she quickly looked away and I think I saw a slight smile; I stood in disbelive, and didn't know what to do, for a few seconds, until I started to proceed to walk away and towards my table where I was studying at; she stood still too.
She was still standing around, with nothing to do around the rubbish bins, when I was walking away. Probably in disbelief that I didn't approach her, even though girls should be getting used to that now since they aren't approached during the day.
It still amazes me that I get so many flirting signals from girls, even thought very few men approach them (if any men at all - I've never seen it during the daytime; and I have only done it three times myself, all of which were short interactions and where I completely failed in asking for their number or any contact details)
....sometimes I just want to kick myself in the balls. I really do.
And especially when I'll be fifty and alone. I'm willing to bet a billion dollars (better yet, make that a million dollars!) that I'll still be intimidated in approaching women then as I am now
[video=youtube]