Discretion & Confidentiality
Often the most daunting part of looking for a new job is that your current employer will find out. Recruiters are experts in keeping you under the radar, it's in their interest to do so.
Searching for a new job is extremely time-consuming and often stressful. Instead, build a network of trusted recruiter connections and have them keep an eye on the market for you.
Access More Jobs
Not all jobs are advertisied, lots are with recruiters only. If you're not connected, then you could be missing out. Better yet, if a recruiter identifies your profile as a good fit for their client, they could even get a job created for you!
Recruiters live and breathe their market. That means they know their stuff - who's hiring, who's paying the best (and worst), who's got the best culture & office. Find out where you stand, and what you could be doing.
A good recruiter knows their client well, and wants you to get the job (that's how they get paid!). So it's in their interest to give you insight to the company and interview tips to help you in the process.
Long Term Connection
Build a good realtionship with several trusted recruiters and they'll last your entire career. Your recruiter will always be on the look out for bigger and better opportunities for you. It's in their interest to do so.