Do you ever follow up on those and see if there's value to it? I get 2-3 messages a week on LinkedIn by recruiters that clearly haven't read my profile for jobs I'm not interested in. I wouldn't consider any of those opportunities.

I get 6-7 messages per week (~1/day on average) and I'd say about half of them are actually recruiting for my skills/location/needs, which is admittedly pretty good for not investing any time into the platform.

I've followed up with a few over the years and they've ultimately not been good fits for me at the time (stack, salary, or location), but I wouldn't say they were bad jobs. Also, for the others I usually just respond with a canned "I'm only looking for X, Y, Z right now, so feel free to reach out again if you find something along those lines!"

I think it's worth having a LinkedIn if you're looking or open to moving jobs, as it's a pretty common venue for recruiters to (easily) get in touch, IMO.