That was Old School terror designed to target proles who are the equivalent of Star Trek redshirts. It works, but the elites don't fear it and in the case of 9/11 even exploit it!
New School, like the brilliant whacking of Alfred Herrhausen by a precision explosive charge or US drone attacks, reaches out to specific high-value targets. For those specific targets the threat is real and coerces them to defend against it. Such attacks don't require an attacker be on the scene making them a logical way to go. Someone wanting to manipulate a pacemaker could put a remotely activated device in, for example, an ordinary looking large plastic electrical enclosure, attach it to a streetlamp or hide it any number of ways, then wait for the target to come in range. It could stay dormant for a long time, even years if power was tapped from a steady source.