Maybe it's because people have the idea that if you and someone else are speaking the same language, then you're communicating. And if one of you seems to have a problem understanding the other, well, it's like the weather, you know. Nothing can be done about it. 
But that's not true. Something can be done about it. 

I'm going to give you 2 principles of communication. Apply them, and understanding will no longer be a problem. Guaranteed. 

Principle #1: You must want to communicate

Sounds obvious, doesn't it? But many people don't want to communicate. Because to communicate is to make known to another what you really think about something. And they don't want to do that. They'd rather deceive, mislead, intimidate, impress, or manipulate for whatever reason. 

Indeed, the greatest obstacle to communication is insincerity. No wonder Shakespeare advised Laertes through the mouth of Polonius: “To  thine own self be true, and it must follow, as the night the day, thou canst not then be false to any man.” 

Principle #2: You must know your limitations

It is not possible to make known to another what you really think about every something. 

For example, you can with cars and airplanes and butter and totem poles and clouds and paper clips and all the other things that exist in the real world. But you can't with psyches and inflation and left-wing liberals and right-wing conservatives and the beltway establishment and all the other verbal phantoms that people mentally create. Why? Well, try as you will, you can never share verbal ghosts with others. Because you can never get them out of your own head.

Think about it.