Capn Bloggs,
Quite simply, the fear/probability of un-alerted see and avoid is greatly exaggerated.
This has been established by every on-the-ground survey done in recent years ---- that the claims of significant numbers of aircraft (always blamed on PPLs, but where in the few cases it happens, "professionals" are almost always the culprits) are not using radio, when operating VFR in G or E, is simply not true.
However, the revised CAR 166 spells it out so there is no "ambiguity" (not that there ever was) about use of radio for communications ----- if its serviceable, it must be used.
Tootle pip!!
PS: What ICAO Airspace? The first class of airspace that meets the design separation assurance standards, and which, by definition, proceeding beyond (ie C instead of E) provides no additional benefit for the additional CNS/ATM resources and other associated costs expended ---- in other words, "economic waste".