Why art is not essential to life?
That's an interesting question, and very subjective, because there are many possible answers and opinions. Some people would argue that art is essential to life, while others would say that it's not, that it's unnecessary and superfluous. While you could argue either way, there are some possible reasons for why art is not essential to life.
First of all, if we define essential by what we actually need to breathe and survive, then only the basics would fall under that category: food, water, shelter, clothing. Those four things are arguably the only things we actually need, that are essential to our survival. Since art is not one of those things, it could be said to be unessential.
Secondly, we could say that art is not essential to life because humans are the only creatures who create art, and in the animal and plant kingdoms, they do not have art and they continue to survive just fine. If there were no humans, the lives of plants and animals would continue and perhaps even flourish in the absence of humans and art. Life would go on, even if that life were not human.
Principally, the point is that art is not part of the basic needs of life. To argue from the other side, however, while art may not nourish the body it certainly nourishes the soul.