Originally Posted by dddc

Might not be as bad as you fear.

Announcements like that will make people wonder what's going on an be more vigilant. This would also make it aware to anyone that may be causing or planning social disturbances that people would be on the look out for it. This could be things like drinking one's own duty free, trying to smoke, being too amorous , sticking feet up on the seats, making advances on the crew etc etc.