I think some of the problem is the complex low level airspace we have in the UK, mixed in with the proximity of many airfields to each other.
If you plot instrument approaches, circuit patterns, holds, extended centrelines, etc. on a map of SE England, it becomes clear that if you fly a route from A-->B, it is virtually impossible not to cross somebody’s patch without weaving left, right, up and down like an inebriated insect.
Add in that you need about five radio boxes if you want to keep in contact with nearby airfields who might have traffic information. It’s little wonder that many don’t bother at all and rely on see-and-avoid in accordance with the Rules of the Air, ACAS, FLARM, etc. It is class G, after all, and just because you’re talking to ATC doesn’t give you a magic +3 Envelope of Protection...