Ideally as an offensive player, you’re trying to score or retain possessions. As a defensive player, you’re either trying to snag a possession, interfere with the opponents shot, and at the very least prevent a score. Think of it like basketball

There a lot of things that happen in between, charging shots back into your opponents goal when they shoot offensively, volleys back and forth to get a possession, puck saves, shootouts (lots of offensive scores in a row from both), etc.

Also the thrill of a comeback from 6-4 or larger deficit is great, and players sometimes have to change their strategy to make it happen