I don't understand why more tech recruiters don't ruthlessly specialize and laser-focus on building a deep understanding of a particular niche when matching candidates and employers.

I'm CTO of a web and mobile development shop with about 20 employees. Finding good frontend developers is REALLY hard - to be a great frontend guy these days, working on modern web apps, you need to have strong engineering chops, with knowledge of the html5 apis, css3 and serious JS experience, including an understanding of memory and performance management in large frontend-heavy apps; ideally have worked on a couple of medium size apps with 5-7 person teams; probably have at least some exposure to the current JS framework scene; ideally (for our stack) have experience with preprocessors like sass or stylus and coffeescript; have good design sense and the ability to work in a collaborative feedback loop with a designer, etc etc. It's a really cross-functional role. There's a lot more people who "know HTML and CSS" but have never worked on serious apps, or have solid JS chops but can't produce design with reasonable fidelity to save their lives.

A relationship with a recruiter who understood this "candidate profile" and could bring me people who would be a good fit, not just resumes with "HTML", "CSS", "Javascript" and "5 years of experience" on them, would be worth its weight in gold.