I've found my most interesting jobs on LI.

Sure, several of them, I could have found elsewhere, e.g. on a dedicated job board. But I wasn't at those other job boards, nor was the recruiter who brought them onto my radar.

If I had avoided LI, I would have missed out on some of my best gigs.

I am not in either of the fields. I get "confidential" offers from headhunters usually on Linkedin or Xing.