I only ever got cold-calls for shitty jobs that I obviously wouldn't be interested in. Every interesting cold call I've gotten has come from elsewhere (e.g. my blog).
Not having a linkedin has, I think, never impeded my ability to get an interview or a job offer.
If your resume is otherwise very weak it might be somewhat useful, but honestly if someone is relying heavily on linkedin in their resume, I'd view that as a pretty bad sign.