As noted in aussie240's
history of the Australian plug, they made sense for safety with the flimsy flexes we had to tolerate early on. With modern (much more reliable) cords, however, I'm not so sure; given that switches
are subject to wear (quality switches should last 10,000+ cycles at their rated load, but still by no means forever), and even breakage if stressed enough (including at the pivots; although a good design should avoid exposing live parts even then, replacement will still be necessary and predictably inconvenient).
In general I prefer to switch on/off primarily with the appliance's own switch (especially for shop vacuum cleaners and the like with substantial inrush current, whose own switches are often higher-rated as well), using the outlet switch sometimes as an additional safety (for items that can be dangerous if accidentally switched on).
Clipsal (our main Australian brand of electrical fittings) already have quite a few 'auto-switched' (the active contact disconnects from mains when the plug is removed) single outlets (and even a twin in their older "Standard" series); although observing their
outrageous list prices, I can understand why hardly anyone bothers with them.
Otherwise the only real problems I can see might be with appliances designed on the expectation of switched outlets.
