IG came to be quite the 'cause' when computers entered filthly electrical systems.
To go down the list:
Crossed over polarities -- far, far, more common than they should be -- so many out there tying their best to give us more repair work...
Over loaded circuits -- until digital logic came along sagging voltages passed largely without remark...
I've never encountered an IG installation in commercial service that was not companion to an isolated power system: an SDS. ( Secondarily Derived Service )
They went together like bread and butter.
It was a LOT cheaper to just drop these in rather than re-work and correct a fundamentally screwed up building -- some of which were bona-fide antiques.
Now that decades have gone by -- and ABOVE ALL -- with the rise of laptops in general office use (which have intrinsic isolated power and secondarily derived services -- every last one) the passion for IG and isolated power has evaporated.
The dirty little secret was IBM figured out they had found the enemy and it was us. Virtually all of the noise in office electrical systems was coming from the switcher power supplies in our equipment. When we put in the line filters we should have been using from the git go, it stopped being an issue.
IG circuits, panels, and receptacles generated a lot of $$$ back in the day.
The search for 'clean power' for the electronics gurus went to motor/generator sets, and active UPS units. That was not your 'standard' offices, but research & prototype EEs in the 'chip making' fields.
My neck of the woods is largely behind the times electrically. I have offices wired in Romex of a marginal utility not connect to a grid, no IG, No surge protection, ground rod and connection to water pipe ground, frequent brown, blackouts, spikes from eagles flying into the lines, diesel generator back up and no problem with electronics. The more protected systems, like IG, ground rings, system wide surge protection, overrides neutrals, and the like seem have more problems. Lol!