Turn Signals are not Always a Polite Request

Yes, a very good video.
Something I learned many years ago on my advanced driving courses was that you needn't give a signal if there is no one around to benefit from it.
Whoa, hold on I hear you say, you should always signal; think about it though, if you are aware enough that you are able to make a decision that there is no one around who will benefit from you giving a signal, then you are aware of what is in front of you, to the side of you, behind you, on the sidewalks (if they exist), all around you, and that was what was really being taught. It's easy to just signal every time you want to make a change of direction but are you really aware of what is around you?
Drive safe.

When it comes to legalities, and whether or not a signal is required, it's important to differentiate between turns and lane changes.

It's my guess that when Section 170 of the Motor Vehicle Act was originally written, many cars didn't have mechanical or electronic signals, or power steering, or automatic transmissions; so expecting some farmer in the middle of nowhere to increase his task load prior to turning off the highway into his farm track, by sticking his hand and arm out the window (no doubt while downshifting and hauling on the wheel) would be an unreasonable expectation if the only creatures around to notice were a couple of crows sitting on the fence.  Hence the wording 'If traffic may be affected by turning a vehicle ... ' etc.

In the modern urban driving environment, some other road user - pedestrian, cyclist, driver, whatever - is more than likely to be affected, making the signal mandatory; and it must be given sufficiently in advance of the maneuver to be effective (so these jerks who sit at a red light and only turn on the signal when it goes green are driving illegally, as well as discourteously).

But by the time that traffic engineers had started creating traffic lanes, automobile manufacturers were providing vehicles with some type of easy-to-use signalling device.  So Section 151 (Driving on laned roadway) Part C is unequivocal; the driver must signal beforehand, regardless of conditions.  And Part A demands that they only execute a lane change if it can be done safely and without affecting other traffic ... but you have to be a fool if you're the 'other guy' and you don't try to accommodate them, I reckon.

When it comes to policing all of this, I have to say I'm puzzled.  Driver behaviours such as failing to signal, following to closely, or hogging the left lane, are frequently cited as major annoyances, even triggering road rage amongst other drivers.  And yet, in more than 40 years behind the wheel, I have yet to see any cop, anywhere, any time, ticketing for any of these illegal and dangerous behaviours.  

And if the police are not part of the solution, is it possible that in fact they are part of the problem? 

Thanks for the input, there is of course always another point of view to consider.  From interest, is there a database anywhere that can be accessed to discover just what tickets are being handed out by the various police forces around the province?

With regard to your traffic court JP, it's noteworthy that back around 1998 (give or take a year) Section 151 (Driving in laned traffic) was quietly amended with the addition of Part (g) 'If a traffic control device directs slow moving traffic to use a designated lane, must when driving slowly drive in that lane only'.

In other words, if there is a sign beside the highway that says 'Slower Traffic Keep Right', and traffic is piling up behind you because you're driving too slowly in the left lane, then you are obligated by law to move over - regardless of whether you're obeying the speed limit.

Being as that self-centred behaviour is not only illegal, but also unsafe as it causes traffic to bunch up (the very opposite of Smith System space cushion driving), one can only wonder if the Highway Patrol have been made aware of it (he asked, innocently).