Audience etiquette

Trev and I have been to West End musicals the last two Saturdays running.  If you were to meet us in the next few days we would probably greet you with jazz hands!  One was Sweeney Todd and the other Singin in the Rain which both originated at the Chichester Festival.  Both excellent but entirely different.
However, this experience has led me to think about audience behaviour.  It amazes me nowadays that audiences in both cinemas and theatres often behave as if they are watching the TV in their living rooms.  In the theatre it especially surprises me as the tickets aren't exactly cheap.  At Sweeney Todd there were two young men constantly checking their phones.  Although this was silent they were causing light pollution and clearly not paying proper attention to the performers but then gave them a standing ovation at the end.  Yesterday, there were two men behind us who kept commenting to each other although Trev's shush seemed to keep them quiet. The guys sitting next to me kept falling asleep and snoring!  I remember going to a performance of the Messiah and a guy in front kept humming along.  People seem strangely unaware of other audience members.
Infact there is a film critic who has a weekly show on the radio and he and his copresenter have issued a code of conduct for the cinema.  I think it should be included in school curriculums!