Why do some men fear of rejection so strongly that they don't even try to get the girl? Shouldn't testosterone be stronger than fear?

GloryQueen
During the years, I noticed some guys like me, but they just text, never initiating anything closer..
They won't put an effort to even try to do something, despite that I am open to see what they want..
So, I give up on them, and after some time, they show up again with half-ass communication, stalking on social media.. I always thought how a typical man would always try something, not hesitating so much. I am always surprised when someone does that. Totally opposite from male instinct.
Why do some men fear of rejection so strongly that they don't even try to get the girl? Shouldn't testosterone be stronger than fear?
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