Answer: Look at how much we produce in the world and how little of what we do brings really good results. As a rule, most of our activities do not have good consequences, meaning fruits.
In the same way, all flora and fauna exist. To the extent that we would treat each other correctly, all plants would bear fruit and bear fruit well. They would give us their fruit exactly in the form in which we could use them.
Yet, since we turn on egoism in our interactions and do not want to treat each other correctly in the quality of bestowal, it turns out that only a small number of our actions have, what is called, a coefficient of performance for a good attitude toward others. As a consequence, we see this in plants as well.
In other words, the fruit symbolizes the end result, the pleasure for which we do some action. Therefore, a person in our world makes a lot of effort in order to obtain pleasure.
If we worked correctly for bestowal, for the sake of the Creator, then every action would bear fruit that we would enjoy. But since all this goes into egoism, we get only some small kinds of pleasures.
Baal HaSulam writes about this: And now, imagine that if we were to collect all the pleasures one feels during his seventy years of life and put it on one side, and collect all the pain and sorrow one feels on the other side, if we could see the outcome, we would prefer not to have been born at all.
From KabTV’s “Spiritual States” 6/14/22