There are several possible motivations.
1. The Canadian government, in 1983, was run by Pierre Trudeau, in the Liberal party. They are the party of gun control. They likely did not want an example where a gun was used defensively during a polar bear attack, to be spread about. The attack could likely have been stopped much earlier, if the workers were allowed more than one gun on site.
2. By 1983, the polar bear had been placed on the endangered list. Unprovoked polar bear attacks remind people that polar bears are dangerous. With the Liberals in power, they may not have wanted to offend animal rights extremists, who tend to vote Liberal in Canada.
3. While bear researchers knew of the attack in 1988, it runs against the narrative of the "harmless" polar bear, as mentioned in the above comments.
OK, because, canaDUH...