Well, for the average person, they don't need to have their cell phone on during church, movies, class, etc. Before the time of cell phones, people got by just fine. However, if a doctor who is on "backup call" or something to that effect has to stay in touch with the hospital, then they are kinda screwed if they go to church on Sunday, or anywhere else where their signal would be jammed. There are professions out there that REQUIRE that people be reachable at a moments notice.
Ryan