Blinkers were always on the outside when most cars had manual transmissions, the opposite would be very inconvenient (and still is).
Then somehow Britain didn't challenge the EU regulation that indicators must be on the left regardless of the driving side.
Japanese and Korean cars still supply right-hand indicatored-cars to Japan, Australia and New Zealand, yet left-indicatored to the UK, go figure, European ones don't give a shit, so buyers of BMWs and MBs suffer (or enjoy?) being incompatible with the rest.
The indicator should be on the outside, so you can change gear (in a manual transmission car) and indicate at the same time. It's just common sense.
I am used to the indicators on the left though when driving my BMW, so I experience the classic "wipers instead of indicators" dance many times when I drive my wife's car. As most cars nowadays are automatics, I guess this reasoning is falling out of relevance more and more.
I also want to note that not all Australian built cars had wipers on the left and indicators on the right – many GM Holden models like the Kingswood and early Commodore models from the 1980s had them both on the one stalk – that stalk being on the right of course.
