Each degree is associated with a career track, but 3 of them are "missing".
For Professional Athlete you need to reach the top level of the Soccer team.
Similarly for e-Sports Gamer you must max the e-Sports team.
Mixology is more obscure; you need to take 11 Mixology skill classes to get a certificate. I was hoping you could get it by throwing enough gold level keg parties, but alas.
Also, for the completionists among us...
Since degrees allow you to choose a career track immediately, if you complete both relevant ones you can switch branches. You need to quit one of the branches first to see the other in the list.
Combined with the Career Hopper perk from Get Famous you can have a supersim max ALL the jobs and jump between them at will.