there's a clue in the name I think. terror, as in deep, mortal fear. the goal of a terror group is to make as many average individuals fear for their lives as possible.

cyberattacks, even significant and disruptive ones, are abstract. it's hard to draw a line from shutting down a pipeline to an individual's sense of mortality. it's not an efficient way to get their message across.

ofc it would be a different situation if terror groups could use a cyberattack to drain the capital out of an entire bank or cause a power plant to go chernobyl.