What is the importance of oxidation process?
Perhaps this is better put on the Chemistry SE page since oxidation is much more important than beyond earth sciences, but I'll give my take on it from an atmospheric sciences perspective.

If oxidation isn't allowed to take place, then the hydroxyl radical ($\ce{^*OH}$), nicknamed the detergent of the atmosphere, cannot remove pollutants from the atmosphere. I think it is evident why removing pollution is a good thing.

This is just one of many uses that oxidation has.