The main reasons in my mind (source: I am Albertan):

1) The oil industry has been a source of high-paying jobs here since at least the 60s; and

2) Royalties from oil are a significant portion of provincial govt revenues.

It's also interesting to note that Canada at large makes up about 8% of all oil exports in the world, and almost all of that would come from Alberta:

https://www.nrcan.gc.ca/science-data/data-analysis/energy-da...

Margins,

Pipelines are a cheaper method of transport that rail and trucking.

It has become ideological politics at this point. It doesn't matter if it makes any sense any more.

No, it’s still the backbone of their whole economy, which has been going through a major recession for years. There isn’t a meaningful number of renewable jobs to take its place, and won’t be anytime soon. That’s going to be the case in any country/region that has an economy built on energy.

The fifth word in your question is also the answer to your question.