Why shouldn't Australia be part of Oceania?

Oceania is a geographic region, which Australia as well as the three main Pacific island groups (Micronesia, Melanesia, and Polynesia). ... While continents have never been consistently defined, what is common across definitions is that land must be part of the same area of continental crust - i.e. read more

Australia is considered by many people to be too big to be an island, which is what Oceania is (a region made up of a collection of islands), and large enough to be a continent (any of the world’s continuous expanses of land). read more

The trouble is that Australia is a large island amongst thousands of mostly very small islands in the Pacific. It is therefore rather hard to create a category for all those disparate and well-scattered islands. read more