Shul, levayas, chupahs, a bris, a pidyon haben ceremony or a shiur where someone’s taking the time and trouble to have prepared to present divrei Torah–it’s not just enough to put the phone on vibrate. It’s disruptive to see people responding and talking when the protocol is to be silent and attentive to the davening or the hespedim and kavod hames or the chuppah, or ceremony or shiur. And let’s not forget about all the texting.
Whatever happened to people just shutting off their phones when entering a venue where talking and texting is inappropriate and out-of-place.
No one has to be available all hours of 24/6 and if someone has such a pressing emergency that needs their full, immediate attention, chances are they wouldn’t be attending most of these functions anyway.