After her freedom from Britain, America ensured her variant of the language was entirely different from the European's.
For some odd reason, Canada seems to emulate America and not Britain. Thus, their writing styles became different.
But Australia, a continent (almost) out of the earth, chose British style.
Despite this, there are over 100 dialects of English, including those of the natural speakers from Ireland and New Zealand, that are yet to conform to the two most revered dialects- AmrE and BrE.
That's why a native British speaker will say "you've drank" instead of the standard "You've drunk" because of disparity.
So, why can't our linguists decide to standardize Nigerian English to some extent. It's fluid and lovely. Like our pigin, it's more regional. Although it will take years to produce materials, teach students, write literatures etc, we can start the step.

You have a point