Quote Originally Posted by Ageofwar View Post
They kind of are mandatory since some of the skills are job quest rewards not to mention there is gear and weapons that are job only

mind you does seem kind of odd they didn't go to the effort of getting there Job Crystal
That person might not even have known that jobs exist. In-game there is very little information about jobs, and nothing at all to indicate how important they are.
The quest that points you to your job-trainer is easy to miss or ignore, and then you never find out about jobs.