None of that applies to an in-house recruiter. Someone who works in HR for the hiring company, directly, may have years of experience, good training, and have a good idea of what the hiring manager is looking for. You shouldn't ignore them, although if you're entirely happy you should have a short message prepared -- "Thanks for thinking of me. I'm happy with my current position, but you never know what the future holds. Feel free to check in with me again in six months or so."
TL;DR: reputation counts.