Some stories or genres require our characters to have certain careers. For example, many types of thrillers need characters with military, spy, or legal system ties. Some contemporary romance series are based on Navy SEALs, NASCAR drivers, firefighters, etc. Some mystery or suspense series follow a private investigator, bounty hunter, etc.
In other stories, our character’s job is like a footnote to their backstory, or it’s simply a way to make the affordability of their living situation believable. (How many “billionaire CEO heroes” seem to never do any work? *rolls eyes*)
Wherever our character falls on that spectrum of job specifics, we need to understand their occupation well enough to know our storytelling options. We might not have a clear idea of how we could tie their job to the story unless we have more insights into their career and what it means for our character.