Why were Aborigines originally excluded from the races power?

Speculation has sometimes been indulged in in order to attempt to divine the reason why Aborigines were, until the amendment of 1967, excluded from the federal races power. Some, including the Chief Justice of Western Australia, have seen in the exclusion a plot to disadvantage Aborigines. However, the whole of Australian history is not a conspiracy against Aborigines; they were not included simply because the races power was directed at imported peoples, which the Aborigines self-evidently were not. Both official and non-official sources from the time of the Constitution's drafting show this, and they also reveal a particular concern, not always lacking in benevolent intent, with the Pacific Islander labourers who had been imported to work on Queensland's sugar crops.