b_sta etc:
I agree with your point about non essential radio calls at CTAFs, however I would argue that an aeroplane overflying at 3600 is "in the vicinity" of the aerodrome, to quote the AIP. Especially given the NDB holding pattern is at 3700 and there is often glider activity to the South right up to the base of class C.
What I would say is non-essential is a call on every leg of the circuit in busy airspace such as CN. Just a call turning base with intentions or turning final with intentions is enough. YHOX had an entry in ERSA suggesting that pilots only make the minimum necessary broadcasts in the circuit for this reason. Not sure if CN has the same - haven't got an ERSA handy.
Furthermore, the old 'locals' who rant and rave on the radio at anyone who dares step out of line or talking about a game of touch footy with the inbound chopper pilots as I heard the other day really is just getting in the way!