The IRA also phoned about many of their bombs. The Omagh bombing is mostly notable because their phone-call didn't accurately identify where the bomb would detonate, and so got people killed.
Plenty of terrorist groups have recognized that killing innocent bystanders isn't good PR.
The IRA usually (plenty of exceptions and changes over time) phoned ahead, they wanted the impact of terrorism without the bad press of civilian killings. Not a particular relevant example in modern times though.
I wonder if it's more about phsycology, someone making a bomb threat is seeking attention for some reason and ignoring it might make their behavior escalate.
https://en.wikipedia.org/wiki/Sam_Melville#Bombings
The IRA also phoned about many of their bombs. The Omagh bombing is mostly notable because their phone-call didn't accurately identify where the bomb would detonate, and so got people killed.
Plenty of terrorist groups have recognized that killing innocent bystanders isn't good PR.