Idk if it's just men. I have had the same happen with women.

It's going to be for the same reason woman aren't, we live on a planet filled with countries and religions who aren't open and honest. This hypocrisy forces some people to live lies just to get by so most people won't be able to be open and honest.

I am

Well, to be honest . It would get in the way of them getting what they think they want. Sometimes they won't be honest because they are waiting it out between a few options and don't want to commit to something until they think its the best deal they are going to get. Women do this too but are just more open about it. a man wants all the advantages he can get. including making you think you have always been number one in his sights. This is how i felt in my 20s. im just being brutally honest. its not something i agree with but.... men tend to think they are at a supreme disadvantage n that they are not actually the ideals women really want. If we were totally open and honest about everything we want , did, or thought. we assume women would usually never speak to us again out of shear offense. so being always in disguise we have to level the playing field by trying to get the very best woman we can get to believe us for just long enough they have invested and are now too close to back out now that they see some of our more horrible flaws. Obviously i don't speak for every man. hell, i may not speak for any of them but me. This was my usual way of thinking much of my life. i believe many men feel the same way and we would never actually admit or agree that a word of this was accurate. that would ruin our chances with who we want to get. live the lie . Deny deny deny. Like Bill Clinton.... I did not have sexual relations with that woman. say it over and over again and we start to believe it. say it a few hundred more times and then even you start to believe it.
No honey i don't find your friend attractive. No i would not like to sleep with her instead. No i would HATE to have her in our sacred bed.
I believe the only way to make a man more likely to tell the truth is to give him the impression you really like the thing he is trying to hide from you. Or sometimes just giving him the impression of a no pressure situation. take it or leave it.. .. so many men are just grown up boys. if you want to get to the truth you have to convince them there is no punishment or negative repercussion .. That or pretend to be overwhelmed by his charm and flatter him.. his arrogance will kick in and he will gladly tell you what he really wants if he thinks you are so anxious to try to give it to him.
I don't know if any of that really helps . But its the truth from a man who is embarrassed to admit this is the actual state of things ..