Slide show effect in 8fps and how to make the best of it

I have an A77 that has replaced my A700 and so far I am very happy with the camera. I am, of course, familiar with the slideshow effect. I don't know if this has been asked and answered yet but with all I have read here I have not read as to why the camera does this? There does not seem to be any reason it should. From what I understand of the EVF it works by receiving light from the translucent mirror and then creating the image you see in the viewfinder or LCD on the back of the camera. Since the mirror does not move when the photo is taken and still receives light, should it not be able to maintain a live view while taking photos? If doing a long exposure, it should also be able to maintain a live view as well instead of going black while the long exposure is taken. To me this seems to be a software issue as surely the camera can be programmed to maintain live view when shooting at 8 or 12 fps. I suspect that the new full frame will not have this annoying effect.