The only importance of career is to select your career based skills. That being said, for your game, are you guys making up your own careers and having your players selecting from just those or the ones in the book? Or are you allowing them to select their own skills and essentially make up their own career?
I'm thinking of making a game where the players are demon/undead/monster hunters. There are two factions that produce hunters, one being solely divine focused relying on holy powers to smite evil, and the other is the arcane faction, understanding how the horrors work and using their own magic against them. I might even call arcane demonic or fel magic for some different flavor. Wasn't sure if I should make up some careers with skills for them or suggest what skills might be important and let the players pick them.