I'm sorry to say it ain't just the pax that this problem manifests itself in.
Once positioned on a non-company flight which happened to have a deadheading crew from my company onboard.
One member read the paper (why give out papers b4 the briefing if you want people to watch!) two had a gossip, and another took 40 winks while the safety briefing was being carried out.
Not on! Poor example to the passengers and most unprofessional to the operating crew conducting the briefing. I dont think I made myself popular when I pointed this out but cest la vie!