There are situations where you are required to use a "box" type mounting for electrical fittings on walls.
Things like dimmers or where there are extra connections at the fitting.
These sorts of mounting plates are used quite a bit these days because they are relatively cheap and fast to fit.
Personally I wouldn't be seen dead using one of them plates, as I've always been taught that wiring needs to be enclosed at fittings, irregardless of there being plasterboard on the wall or not.
Them dwangs you see in the pictures are installed at half wall height (4') to strengthen the studs, now unless you like your art down low on the wall, you'd usually be driving nails into a stud, would you not?
Besides, there are so many easier ways to hang pictures and things on walls these days without using nails.
One other thing needs to be said, down this way, we use 230-240V single phase, consequentially our wiring carries half the current of an equivalent 120V circuit and hence the wires are also smaller.
Our terminals at fittings are quite a bit different to the ones used in the US as well.
Instead of putting a wire under a screw, we have "tunnel type" terminals, these are very handy where you need to terminate more than 2 wires at a socket-outlet or light switch, it also means we don't need to "pig-tail" any of our wiring at fittings.
Provided the screws in the fittings are adequately tightened, loose or faulty connections are pretty rare.