Some people dont know the differnce between carrying a phone , turning off the ringer and checking it every 2 minuets. And no not everyone needs to carry it on shabbos, but at least 2 people in every shul (Usually doctors) should have access to one in case of an emergency. Like I said, Ive seen it happen more than once.
And Once it looked really scary. Thankfully one of the doctors was there , and was able to call Hatzolah