Sarcasm doesn't allow the person who were told it to express his/her point of view.
In order to understand the action of the person, you need to understand his/her point of view. By communicating with him/her and creating a dialog, you can understand what is actually happening.
Human behavior or emotion is very difficult to guess. Even in the controlled psychological lab environment eliminating as many unrelated factors as possible, it is difficult to pinpoint the causality of the behavior, emotion, or reaction. In the real world environment, it is almost always true that the observer's experience, emotion, knowledge, etc. biases the observation. Not only that, the person who is being observed behaves differently depending on the circumstances he/she is in. So it is certain that the observation is wrong. Hence, sarcasm is useless, which is solely based on the observer's point of view.
Also sarcasm makes the topic appear to be more important than it is at the moment. Even when there is another important thing that is worth, say, 80% of the person's attention - e.g. software code that is used 80% of the time, etc. - if somebody says sarcasm about a topic that is worth only 20% of attention, that topic gets the major attention or even exclusive attention. That's harmful.
And if the person who is told sarcasm says something back, all the person who said sarcasm has to say is that he/she not talking about the person who is told sarcasm. In other words, the person who says sarcasm doesn't take a responsibility of what he/she says. So often times, the sarcasm is ignored by the person who is told the sarcasm. Who would take a comment seriously made by somebody who is not willing to take a responsibility of the comment? That's another reason whey sarcasm is useless.
Life without using sarcasm is much tougher and requires intelligence and discipline, which is the opposite of some people's belief that using sarcasm is a sign of smartness. And life without sarcasm is much more productive and fulfilling.