@StarFleet Carl
Because the holes in the shielding around the microwave are smaller than the wavelength of the microwaves generated.
Hence, a Faraday Cage. That is actually the technical term for it.
And you can make one at home using nothing but a galvanized steel trash can. Some paranoids even install Faraday Mesh fabric (a real thing, under $20 a square yard) in rooms in their house.
Heck, a lot of older computers really were Faraday Cages. It was a requirement to prevent leakage by the FCC. And a lot of your higher end server racks still are Faraday Cages.
You're simply refusing to accept one relatively minor, nearly insignificant detail. CIVILIAN BUSINESSES DON'T CARE!
Oh, they go by the fancy name "RF Shielded Server Racks", but they really are the same thing. Not at all uncommon, or rare. And putting a second Faraday Cage around a server cluster is also very common, as it also protects from a lot of other things, like all the RF thrown out if a transformer blows up or extreme sunspots (or the placement inside of a transmitter to be used in "man in the middle" attacks).
You have to realize, I have been dealing with these for decades. And civilian businesses do care, because it is cheap insurance against many security issues. Even more so now as many are moving to locking faraday cage racks as part of their cybersecurity system.
https://hollandshielding.com/RF-shielded-racks
The cost to actually add a Faraday cage to a 10 yard by 10 yard server room? Just a few thousand dollars, it really is not that expensive.
Hell, I have even seen "accidental Faraday cages" on more than one occasion. One of the funniest was when a construction company brought me out, because their new wireless router could not talk to a building only 50 yards away. I went there, the router was literally inside of an on-site construction office trailer, inside of a sheet metal building. Faraday Cage. I got an external antenna, put it outside the trailer, and it worked.
And I have heard those arguments before. But it is almost never true, especially when you are talking about the IT infrastructure. There is a reason many IT Managers in smaller companies are also the Disaster Manager. And why IBM ruled desktop computers for a decade (and mainframes before that). Sure, a System/360 cost a hell of a lot more than a PDP-10. And an IBM AT cost a hell of a lot more than a Compaq.
But as the saying goes, "Nobody ever got fired for buying an IBM computer". Companies shell out a huge amount of money for these systems, and absolutely rely upon them for daily operation. "Spending an extra $500+ per rack for shielding? Bah, don't even bother bringing it up, just order the thing if you think we need it."
Oh, and notice I did say "military-government contractors", as the government requires most contractors to take these safeguards. And many do it themselves, to help prevent not only hacking, but corporate espionage.
And most equipment does not need to be shielded, just the critical stuff. Yes, a lot of stuff will need to be replaced, like say the electronic switches on the pipeline itself. But not the system that runs it.
And I can promise that more is shielded than that, because TEMPEST requirements go all the way back to WWII. When Bell Telephone proved to the military that they were able to intercept clear text transmissions of coded information by analyzing the power use of the systems doing the encryption and decryption.
Faraday Cages, TEMPEST, and a great many other technologies still used today long predate the recognition of EMP. Even going back to when an "atomic bomb" was just a figment of the imagination.