Having a clean gun is paramount to keeping a functional firearm. If you don't make a point to maintain your firearm, then you won't know how/when to inspect it for wear, tear, damage, corrosion, erosion, rust etc.
There are things that can happen to your gun that are so subtle, that if you aren't trained to look for it, you won't notice it, and if you don't notice it.. you could blow up your gun. Using the wrong cleaning products can rust your firing pin and barrel overnight, and over lubricating your gun can cause it to catch on fire!
All these things can be prevented. Just learn how to clean your firearm. Read your owners manual! And use quality ammunition doesn't hurt.