Why dont men talk plainly instead of in circles?

Why are men so hard to get straight answers from? When I'm talking seriously to this guy about what he wants he always tells me that he doesnt know. But then when we get in a disagreement he tells me I dont know what he wants that all I do is ume, how can you get them to be straight forward with you especially when it comes to needing to know if he wants to be with you or not? He says and acts like he does but his actions are totally diff. than his words and when you try to get him to spend time with you he is always busy or has someother excuse. How can you get a straight answer?