Why is it so hard to listen?

So last week, our class read a passage about the habits of mind.
Listening to others with understanding and empathy was one of the habits.
They called listening a complicated skill.
But why is listening so hard?

In the passage, the text states:
"This is a very complex skill, requiring the ability to
 monitor one's own thoughts while attending to someone
 else's words."

There aren't very many steps to actually listen and understand what someone said.

Here's a video that are really the steps on how to listen:

I just don't understand why they call listening such a complicated skill...

But on the other hand, reserchers suggest that humans only remember 25-50% of the things we hear.

Maybe we only hear so much of a conversation because a lot of people doze off in the middle of a conversation. If the topic is about something I'm not really interested in, I wouldn't really pay attention. But I think humans need to learn that not all topics we like will be discussed during class or during any conversation with a friend. 

Basically, the only steps to be an active listener are:

1.) Pay attention to what the person is saying and be sure to make eye contact.

2.) Show that you are listening by either nodding your head or say something relavent to the conversation.

3.) Share your opinion AFTER the person you are talking to finishes speaking their thoughts/opinion.

It just came to me that it's not actually THAT hard to listen.