Why would a guy keep his girlfriend secret?

Anonymous
A guy friend of mine in his mid 40's is very careful to keep his girlfriend a secret. He has been seeing her at least 6 months, keeps his Facebook status as "single" and when he rarely talks about her it is "my friend" or just refers to her as "her", but no name. He is also careful to not post pictures of him with her.

I'm pretty sure they are probably sleeping together. I think she is in her 30-40's too and I know he does a lot for her. I know that at least his sister and some friends have met her, but everyone seems so mum about her? She is just an average girl, no one famous, not married?

Why so secret then and keeping her identity such a mystery? Even if it is a somewhat new relationship? Guys and girls, why would he keep this relationship so secret? Wouldn't you want to sing it to the world if you were in love or even just dating someone you were really interested in?
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+1 y
Wondering why no guys will answer this question. Don't want to reveal the secret? I think that he won't call her his girlfriend because he has already decided that she won't fit into his long term future plans.
Why would a guy keep his girlfriend secret?
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