Not talking about movie theaters but the regular kind. In Estonia going to a theater or to a concert in a concert hall (sitting down, orchestra etc) is atleast a semi formal event, you put on your evening clothes (perhaps not necessarily a suit but usually atleast a dress shirt for men), leave your overcoat in the wardrobe, maybe have a small coffee or cognac before the show or during the intermission. But generally everyone is quiet, absolutely no talking and definitely no phones. This applies to grand dramas but also for comedies and experimental theater alike.
However I have noticed while going to a musical in London, to an opera in Rome and as well as have heard from others that things are quite different in other countries. Theaters are still very nice and fancy but I saw people with their outdoor clothes sitting inside eating snacks during the play and the opera house in Rome even had a functioning bar to use during the play or you could even order food to some seats. All in all a much more casual experience even if the dress code was still formal in the opera.
I've heard from somewhere that the difference might be down to a legacy of the Soviet Union where you had to follow higher standards etc. Even if the dress code changes (don't want to make that the main part) the whole experience is still undoubtedly formal.
What is it like in your country, is there a difference between "eastern" and "western" europe?