Maybe they don't explain it in the article, but I'm gonna posit my own two cents: Alberta's economy is quite big, relative to how much it contributes to Canada's GDP as a whole, but the overwhelming majority of that is in oil and hydrocarbons, and a lot of the overall economy is geared towards that particular industry. Without it, Alberta would be in a significantly worse position. I would wager that we are seeing a good example of Dutch Disease.
What Ontario and Quebec lack in oil, they make up for in a more diverse economy, especially being the economic financial and trading hot-spots a la Toronto and Montreal. They have a robust enough economy that they can basically support their own dedicated Provincial police force and not have to rely too much on one singular economic output to fuel the entire thing.
With the EV market looking to expand faster and faster, Alberta hitched its economic future on a product that people actively want to turn away from. To create their own police force would mean they'd need their economy to be capable of funding this police force permanently, no Federal assistance, and if the demand for oil craters out because more and more people start getting off gas and going towards EVs, heat pumps, nuclear / solar / wind, etc., well, then Alberta would be quite pooched. Also, worth pointing out that neither Canada nor Alberta have enough weight in the global oil markets to guarantee that oil is a prime economic benefit, especially if new sources of cheap oil start popping up in the US.
I can't speak to all of the political reasons for wanting to create a new Provincial police force, but economically? Alberta is better off relying on the RCMP rather than trying to do its own thing, just in case funding becomes a problem in the future.