Im going to put it this way.
Take a look about you. Atoms make up everything you see, hear, touch, taste, smell, and even your own body. Atoms are responsible for everything you do, think, feel, want, and decide. They join together to form molecules, transmit electrons, and emit and absorb light. Some aspect of "atomic theory" describes all of these functions. With a few key exceptions, everything that happens in the world is based on atoms and "atomic theory." Light, radio waves, wifi, phone signals, and other communications all propagate in different ways. Gravity is as well. However, all matter, whether living or dead, solid, liquid, gas, or flame, is made up of atoms acting according to "atomic theory."
What could be more essential than that?