@Shalvenay Because we repair industrial equipment, some of it in the tens of kilowatts. An isolation transformer would be incredibly expensive, times the number of techs.

Tek did make an isolated scope - where each channel was completely isolated - TPS2000B, but it was one of the low-end models only, and its discontinued.

Fluke makes a handheld battery-powered oscilloscope with independently isolated channels.

We do have one of those, which floats around the shop. Very nice because even the BNC shells are insulated - no metal exposed anywhere.