why are young male employees so hard to talk to?

Although, I have noticed that fewer young people these days know how to converse much less how to interact socially compared to previous generations.  I think the problem is how you were trying to strike-up a conversation.

To converse, you ASK. You do not just throw a comment out there and expect a conversation to commence. First, although you seem like a fair reasonable boss, you are nevertheless The Man. If you say the sky is purple, do you really expect your helpers who do not know you well to start a critique? They need the job and they are not going to do anything to jeopardize it.

Maybe, after they have come to know you well, they will be more free with their opinions and speak freely with you.  But that requires earning their trust. And as generous as pay, drinks, and food is, it really does not tell them who you really are.

Im way older then you and never had much problems communicating with men or women until smart phones became glued to everyones hand. There  is a generation of kids that have no social skills, so what do you expect? Its like getting water out of a rock, so good luck with that.

What are you asking them? They probably only play video games and if you aren't asking them about that then you are going to get silence. No but really just find out what they are into and talk about that and see if they respond better.