I work on short haul in Europe mostly scheduled flights and occassionally charter. Our demo is done by the crew (not enough space for a video) and interestingly our charter flights pax are always the most attentive, and how shirty do business pax get when you ask them to be quiet during the demo. My thinking is the reason we do a demo before take off is that something may happen during or shortly after take off and the crew haven't time to prepare the pax. Also after our demo I'd love to go down the A/C and ask them where the 6 exits are.Watch the blank faces as they try to work it out, ' Theres only four sir, but you wouldn't know because you didn't watch the demo.'