What are the possible reasons a guy hides his relationship?

So we have been colleagues and friends since the last 6 months... We texted on a daily basis with details ("good morning, good night, I will eat now, I am having a layover in New York and my seat number for the next flight is 6-C, you will ace the interview, I believe in you" type). I like him a lot and I think he knows. He always avoided meeting outside of work or public places. I recently found out that he has a girlfriend and was baffled. When I asked him why he did not tell me he gave me some nonsense answers like "you never asked". When I told him that I thought we were good friends he got angry and tense. I always thought if we were close friends he would not avoid meeting outside (because that is normal) and that he could be hiding something, but never imagined that would be a girlfriend. Why do you think he was hiding? What are the reasons guys hide something like this?
What are the possible reasons a guy hides his relationship?
6
4
Add Opinion