Just returned from a trip to the USA, and what struck me in the light of this thread was the number of incorrect read backs, and misheard frequencies, along with quite literally dozens of: "........I missed it - who was that climbing to '4 oh oh'?" or ".......sorry what heading was the Cactus on?" type of confusions I heard, because just about everyone was using non-standard phrases.
Yes, using ICAO standard phraseology does make us all sound a bit like spanners, and it probably does sound much cooler to say something like "Monck centre cactus three oh four checkin in descending two six oh smooth" and one can just imagine the square jawed, handsome pilot wearing Wayfarers who says it.
Particularly intriguing though I would have thought, is the risk of lawsuits in the USA, making me wonder why folk would potentially leave themselves wide open to the lawyers in the event of a mistake caused by use of non-standard RT? Or wouldn't this apply?