The easyJet demo is fairly standard in that very few make a big point out if what to do with luggage. It's been many a year since I flew them but I'm fairly sure United would mention in before take off and then once again on approach "if an evacuation becomes necessary, leave everything behind". Still, you could advise people individually or have a big flashing sign telling them not to haul their carryons off in an emergency. Life is cheap nowadays, and people are more self centred and lack any sense of responsibility, particularly in the UK.