Just a theory but generally bigger brakes are suited to heavier cars ie.
Lambos which are capable of much higher speeds and require the additional heat dissipation.
Same goes for the Micra brakes
- a K11 Micra is about 800kg so probably uses tiny bottlecap discs
(and probably drums on the rear?) Our MR2's only weigh 1300kg ish
(if not less) so are not exactly heavy cars by modern standards.
Also with Lamborghinis, R35, Ferrari etc.
there is a certain requirement to go a little overkill on specs, such as 400mm carbon ceramic brakes, 8 pot calipers and floating discs etc.
which will generally never come into their own on the road
- however the customer is expecting a car which offers the best of all the available performance parts and pays a premium for the privilege.
I'd hazard a guess that a lot of it is brand image, although they are obviously race cars for the road so I'm not entirely discounting the purpose of these parts.
I bought my MR2 already fitted with 4-pot front calipers and they are epic, but I noticed a HUGE difference after investing in Yokohama AD08R's.
It seems to be increasingly common that owners are driving MR2s on cheap crap tyres and then complain that the car is rubbish.
IMO you should start with decent rubber and wheels if you want to get the best from your car
(incidentally I'm selling two sets of VERY deep dish Works 17's that'll fit with wide arches if you're interested.
Drop me a PM!)
EDIT forgot to mention that my calipers still use standard discs, but custom-size Carbotech pads.
Decent pads will change your life