Why do I ask? Just because I've been wondering for a fair while why a complex, fragile, mechanical device with limited performance (the shutter) is still required when just about every other mechanism in cameras has been replaced by an electronic solution. And because it seems to me that electronically controlling the "shutter" could give big advantages, e.g. reduced cost, silent operation, extreme accuracy, very high burst rates and potential special effects. Plus the possibilty of live view via a semi-silvered mirror, as in the old EOS RT, where the mirror doesn't have to move. These would seem to be huge benefits, so what's stopping it?
As you say, it's done in fixed lens digital cameras, so why not SLRs?
Is it to do with protecting the sensor from dust while changing lenses? Surely a simple cover which flipped out of the way with the mirror would do the job?
Protection from the sun? Well, point and shoots are exposed, as are video camcorders.
As for lack of imagination on the part of camera makers, that can't be it, surely. Olympus, especially, are well known for thinking sideways, and Minolta had some great innovations.
OTOH, if any manufacturer wants to contact me to discuss royalties on my idea, feel free, gentlemen.
No, there must be a more fundamental reason, I assume, or someone would have done it. Wouldn't they?
Pete