The Gemara on Amud Aleph states:

⁦Rabbi Yoḥanan said that the verse states: “You shall prepare for you the festival of Sukkos for seven days as you gather from your threshing floor and from your winepress” (Deuteronomy 16:13), and the Sages interpreted that it is with regard to the waste of the threshing floor and of the winepress that the verse is speaking. One uses grain stalks and vines for roofing the sukka, materials that are not susceptible to ritual impurity and grow from the ground.

I will share an idea partially based on a Sod Yesharim (Succos 87). The schach is made from the shells and husks of the wheat,and the branches from the vine. The symbolism behind this is as follows: A person who consumes the wheat may wonder as to what purpose are the husks? In other words, sometimes we are tempted to only appreciate the direct benefits and pleasures we receive in this world, but we resent the complications and technicalities. The schach of the Succah that represents Divine Providence is specifically from those husks to emphasize that we need to appreciate the background story behind the pleasure and Providence of this world.

We cannot really enjoy life without the struggle. We think, “Oh, life would be great if I had everything I wanted.” It’s just not true. You would be miserable if you had everything you wanted, and I’ll prove it to you. Humans simply thrive when they are met with appropriate challenges and surmount them. They wither and die when either having it too easy or impossibly hard. Consider the following thought experiment:

Imagine we could kidnap a random person on the street, and hook him up to a special machine that dispensed euphoria-inducing drugs while keeping him alive on some kind of life support. The person would be able to spend every remaining minute of his or her life in a state of ecstasy. Let me ask you, would that be a fair and dignified way to treat somebody? Would you want that to happen to you? I assume you would say no. If so, you must ask why? After all, you experience endless pleasure until the day you die.

If you truly believe you’d be happy in that state, and that is really what you seek, maybe you are right then, but most people would feel creeped out by the idea of having pleasure with no challenges or autonomy. In any case, it would be an impossible state to achieve because our very physiology is wired not to work that way. What goes up must come down. The Neurochemical responses that produce ecstasy at some point become depleted. This is why the cycle of drug use, especially strong euphoria-inducing drugs, in the end, also produce a terrible low. Psychologically speaking, it’s known as the law of conservation of pleasure. You can only eat up to a certain point without feeling disgusted with food. You can only have sex to a certain point without being disgusted with it. It’s God‘s plan, and probably even more deeply, it is an immutable truth of the universe.