This may be partly due to the infamous "dubplate culture" intrinsic to the Drum n' Bass scene, and later the Dubstep scene. Back in the late 90s it wasn't uncommon for certain gigantic tracks to exist as exclusive dubplates given to only top-name DJs for a couple of years before their eventual release... tracks like Bad Company's "The Nine" being a prime example (Prototype was a label notorious for this kind of hype-building tactic).

These days, the tools and techniques of DJing have been largely demystified, so DJs and producers trade in a currency of unreleased tracks, otherwise there's precious little to differentiate their sets from those played by any number of technically qualified local DJs.