There are several arguments for consistent use of the serial comma:
1) The use of a serial comma better matches the spoken cadence of sentences.
2) Using the serial comma can resolve ambiguity within a list of ideas.
3) Its use is consistent with other style means of separating items in a list.
On the flip side there is one strong argument against consistent use of the serial comma:
It is redundant in a simple list, because the and or the or is often meant to serve (by itself) to mark the logical separation between the final two items, unless, of course, the final two items are not truly separate items but are two parts of a compound single item.