Modern lifestyle + chaos’n’wrecking = FIRE!!
whether the chaos’n’wrecking is supplied by a hurricane, earthquake, landslide or giant rampaging gorilla affects the size and frequency of the resulting fire, but the principle still holds. Lots of flammable stuff and various energy sources all piled up in a heap and stirred about as though with a giant stick tends toward burnination.
Because then you also shut off power to fire alarm systems (which have to switch to backup battery power), as well as sump pumps and stormwater dewatering pumps (which are needed to mitigate the effects of flooding), as well as water utility pumps which maintain water pressure (which you need to fight fires), along with wastewater pumps (which are needed to keep sewage from backing up into the streets and into people’s homes), etc., etc. You also cut off all lighting in the city, which makes it more difficult for emergency personnel to maneuver and fight fires. As my family in Houston can attest, it gets very dark when all the lights go out.
Many of the municipal pumps I’ve mentioned have backup systems (such as diesel generators), but they only have enough fuel for a finite period of time.
That would be unfeasible for Gas. Purging the entire system would take a very long time and would require an incredible amount of air pressure. The utility would also have to physically turn off, turn on and relit the pilots for every single customer. For an outage of a hundred customers this is a sizable task. On a regional scale it would be astronomical.