They're governed differently because so few people live in the far north, and so much relies on federal money anyway. A territory would need hundreds of thousands more residents and a much bigger economic base in order to justify the effort of amending the Constitution to make it a province.
The Quora answer overhead doesn't fully answer the titled question. If these territories' populations and GDPs per capita are too scant, then why
weren't these territories fused with provinces (e.g., YT into BC)?
Source: The Canadian Justice System: An Overview (2017 4 ed). p. 18 Top.
TERRITORIAL GOVERNMENT POWERS
Yukon. Northwest Territories and Nunavut have a different legal status than the provinces. Though the powers the territorial governments exercise are very similar to provincial powers, there are differences, even among the three territories. Rather than receiving constitutionally protected realms of power, all three terri-tories are created by federal statutes, Yukon Act, Northwest Territories Act and Nunavut Act respectively. Section 18 of the Yukon Act, section 16 of the North- west Territories Act and section 23 of the Nunavut Act, list powers that can be exercised by the territorial governments (called Legislative Assemblies in Yukon and Nunavut, and Council in Northwest Territories). These lists borrow their wording directly from the powers listed for provinces in sections 92 and 93 of the Constitution Act, 1867, but also add some unique features. Because they are bestowed by federal statute, powers could be taken away or added by the federal government without going through the complex amending formula process that would be required to change the constitutionally protected powers of provinces.
All three territories have some law-making powers that have not been specif-ically addressed in the constitutionally assigned powers granted to provinces. For example, each territory can legislate in relation to "intoxicants" (because of clause in the Yukon Act, clause 23(I)(p) in the Nunavut Actand section 49 in the Northwest Territories Act). The Northwest Territories and Yukon have both been granted a power to levy a tax on furs, through clause in the Northwest Territories Act and clause 18(l)(g) in the Yukon Act. This issue is not directly addressed in the Nunavut Act. The Northwest Territo-ries are granted a unique law-making power in relation to the herding of reindeer in section 45 of their Act, while Nunavut's government has responsibility over the preservation of the Inuktitut language due to clause 23(1)(n) in their statute. Yukon and the Northwest Territories have an enviable power. like that granted to the provinces in section 92A of the Constitution Act, 1867. to make laws in rela-tion to the exploration and extraction of non-renewable resources (section 19 of both the Yukon Act and Northwest Territories Act), Nunavut has not yet acquired this power through negotiation with the federal government.