Question

why is the removal of the combustible material not always possible when extinguishing a fire

Answer 1

because combustible substance is hard to take when its burning,we can only reduce the temperature

Answer 2

Why is removal of combustible material not always possible when extinguishing fire?

Because if there is a fire on the building where every object is combustible material then it is not possible to extinguish the fire by only removing the combustible material.

You cannot remove the combustible material out of building the only way of doing that is using of carbon dioxide extinguisher or water.