According to Wikepedia, "Materialism is a form of philosophical monism that holds that matter is the fundamental substance in nature, and that all things, including mental states and consciousness, are results of material interactions. According to philosophical materialism, mind and consciousness are by-products or epiphenomena of material processes (such as the biochemistry of the human brain and nervous system), without which they cannot exist. This concept directly contrasts with idealism, where mind and consciousness are first-order realities to which matter is subject and material interactions are secondary."
At first, it seems to make sense. Much of what we encounter is material. Our food, light, furniture, etc. is all material. It would be easy at first glance to think everything boils down to what is material. But, does that really comport with what we experience and know?
Materialism leaves out a large chunk of the human experience. First, it fails, like naturalism, to fully account for the supernatural and the spiritual. And, in doing so, it denies free will and many other parts of our experience that are products of the spirit.
Also, materialism doesn't allow for the abstract truths we know to be. Moral truths, natural laws, beauty, and even some mathematical truths can't exist if everything is material. So, materialism fails to explain all that we know about the world.
There is more to the world than just the material. It doesn't fit with our understanding of the world. We experience more than just the material in art and music, as well as abstract concepts. We also experience the phenomenon of free will, which is impossible in a materialist world.
In order to fully comport with reality, we need to take into account more than material things. In order to fully experience the world, we have to take account for the non-material parts of our lives.