Why is fuel needed to change the speed or direction of a probe in space?

Newton's first law of motion clearly states that once an object is traveling in a direction, that object will not change its direction or speed until something slows it down, stops it, or makes it change direction. Outer space creates a void where using a fuel propellent is the only way to move a probe.

Fuel is use to produce a force to accelerate in a new direction. In the void of space the object will continue its velocity until somthing acts upon it. (newtons first law of motion)