Bloggsie,
You have the answer, but can't see it.
Quite simply, there are not legions of pilots out there who want to fly around "no radio", this is all a myth, and all the research shows it is a myth. Likewise pilots operating in "stealth mode", to avoid charges, largely a myth.
Most of the identified cases (with one exception) of "non-compliance" have turned out to be finger trouble, the biggest "offenders" are those most likely to be "there" ---- professional pilot, like the SAAB crew recently in northern NSW, all the calls were probably wonderful, pity all they did was turn the lights on. Nothing intentional, just what most of us have probably done from time to time. Center just loves passenger PA's on frequency, particularly when the hapless sod announces his/her name to the several (in US-- several hundred) others on the same frequency. Welcome Captain Speaking, the world's best known Captain, anybody remember the "Captain Speaking" trophy over the old Bushie's Bar?
The "exception", ag. pilots at several centers (CTAF(R))---- not the dreaded "blundering bugsmasher" ,"Weekend Warriors" etc. By and large, this is one area where all pilots, regardless of license (or certificate) type, have been consistently shown to exhibit a very good level compliance and, in my experience, CBS.
But you will have to look at the records of the last Safeskies to learn about CBS.
As McCormick correctly stated, there is a demonstrated 96-98% compliance with radio calls at all CTAF/CTAF(R) for all aircraft, not just with those with a radio.
Three studies, all conducted at considerable expense, over about a 10 year period, all coming up with essentially the same findings ---- but some will never accept such challenges to their belief system, that's their right, your right, but no basis for rational regulation making.
McCormick is on the right track. Evidence/fact based rulemaking, not anecdotal war stories.
Tootle pip!!