What are the career fields where you definitely don't need a LinkedIn?

Some might say that no one needs LinkedIn at all but there are some jobs that people struggle to attain so they get on LinkedIn. I have noticed though that I've mostly seen users who are in things like tech, marketing, business, and blue collar jobs on that platform. I didn't see many people on there who work in medical professions but it could have just been a tailored experience for me. Are there career fields where you wouldn't even think about making a LinkedIn?