In a person-to-person world, the way that we communicate is through talking, but for everyone that talks, there must be at least one person that listens to what has been spoken, or we are essentially just talking to our own self. Not too surprisingly, most people that speak believe that what they are saying has some sort of merit or worth, or else they probably wouldn't be speaking, though there are exceptions to this rule, in which some people like to talk and talk, mainly because they can't seem to handle silence or solitude, but in any event, those that speak to others, are expecting and anticipating that those others that are hearing their words are actually listening, though not all that is spoken is ever actually listened to.
The fundamental problem with a person talking, is the preconceived notion that they often have, that they other person is prepared and desires to hear what they are saying, in which this is not always the case. In fact, many people that seem to appear to be listening are really only listening for their opportunity to have their own say, perhaps which ensues, during a pregnant pause or similar. Further to the point, some people listen only in the generic sense of showing a basic sort of courtesy, but aren't really taking in the words, except to acknowledge a general affirmation or consent, that they have heard the words so spoken, but really haven't taken in the words. Additionally, those that are ostensibly listening, might actually have a desire to really listen, but are at the present time overwhelmed with their own troubles and problems and therefore their mind is not properly prepared to listen to what is being said. All these, are examples of people that aren't really listening, of which, the speaker of the words, may or may not, be aware of their lack of attention.
While there are many reasons why people do not listen well, of which some of those reasons, have justification; there are those other reasons which really aren't justified at all. For instance, some people do not listen well, because they dismiss what the other person is saying because they have no respect for that person, or don't care for that person, or don't value that person, or simply because they don't believe that anyone could ever possibly tell them anything of importance or value. Anytime, that we marginalize another person, especially when that is done, under the perception that we are more important than they are; then any possibility of good communication from one person to another is not possible. Further, a lot of what appears to be communication isn't communication at all, but basically each party, taking their respective turn, to talk past the other person, and hence no common ground is ever achieved.
The reason that listening well is so important, is that the very point of communication is to impart information, and while some of that information may be of marginal value, some of it also may be of immense value, and therefore, those that believe that experience is always the best teacher, seemed not to have understood that learning well, encompasses listening well, so that those that go furthest in life, aren't necessarily the smartest or the brightest, but rather are those that are able to focus their attention upon those words spoken, and by their attentive listening as well as their astute discernment to do right with them.