Why would someone want to be so unbelievably secretive?

So my crush seems very secretive. He’s a really good looking guy and confident but he doesn’t let much out about himself. He keeps conversations open but doesn’t get personal. many of his guy friends on Facebook follow loads of girls but he only follows a fair few.

He has 2 Facebook accounts. On one he has a few pictures but only follows people he knows well and has changed his settings so that no one can search him. On the other he has around 300 people but has no profile picture and just a black image. So seems like he’s comfortable with people seeing his pictures who know him but others not. His Instagram is private and he only allows people to follow him who know him and just has one picture.
Why would someone want to be so unbelievably secretive?
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