Building, maintaining and operating a plant is costly. Perhaps the locations of their towns are not amenable to wells + simple chlorination/uv, I don't know.

But, I have heard it's not the costs that's the biggest problem. There's something in the agreements with the feds that if they fund it themselves, they get less money (for other things?) in the years to come. It's highly incentivized for them not to do anything themselves.

If you read in this article, the standard is for the feds to provide all capital costs and 80% of operating costs. https://atlantic.ctvnews.ca/mobile/atlantic-first-nations-create-water-utility-to-be-up-and-running-by-2022-1.4996605

Good on these atlantic first nations to re-negotiate and come up with a more independent plan.