Because the EOS 300D series are digital SLR cameras, and not video cameras. Also, filming a full 25 frames per second, for a whole day, would use up ~10 tapes. Normal video plays at 24, 25 or 30 frames per second. If you want to speed the 8 hour video down to 3 minutes, you'd have to play it at 160x the speed, or 4000 frames per second... But you can't, I'm pretty sure there are no film projectors that fast, or any computers fast enough to handle the massive amount of data. 25 frames per second is considered smooth enough by most people, it's what everything in PAL is these days. 3 minutes of 25fps video is 4500 frames. If you want that spread out over 8 hours, you'd have to take 0.15 frames every second, or one frame every 6.4 seconds. Also, as you capture DV in real time, you'd have to sit and watch 8 hours of footage being captured, and change tapes every hour. How boring would that be?!