Because no emergency call will ever be sent to a telephone within 30 feet of a jammer?
OK, that's silly.
"Nobody is going to die because of a jammer." That's nutty too. What about "don't take your meds there's been a recall" "we can't find our daughter, have you seen her?" "the bad guys are after you, get yourself to a policeman for protection immediately." etc.
Further, what happens when the badguys start using jammers as part of their MOs? Rape/murder in a parking lot at night is so much safer when you can discount a speed dial 911 call from the victim.