The moon isn't really there for no reason;)
Other planets beside earth do have their own moons as well.
Our moon gets its light from the sun, therefore its rule seems superficial and redundant in comparison to that of the sun, yet it does have some functions among them the control of the ocean's tides with its gravity, without it, there would be tsunamis for no reason.
The moon helps also slow down the rotation of earth,without it the day would have been very short.
And if it disappeared?! The earth might risk flipping upside down.