Because the Europeans conveniently decided that ingenious populations didn't own anything: http://en.wikipedia.org/wiki/Terra_nullius http://en.wikipedia.org/w

Because the Europeans conveniently decided that ingenious populations didn't own anything: http://en.wikipedia.org/wiki/Terra_nullius http://en.wikipedia.org/wiki/Terra_nullius Ok, so that's more "how" than "why". The "why" was because they wanted it.