This thread seems to have deviated quite a bit from its original course.
Let me now split it into two different directions.
Earthed/Un-earthed Scopes
Nigel is happy with his un-earthed scope, many others, myself included, much prefer to keep them earthed for reasons of electrical safety. That is OK.
But consider, chassis of the un-earthed scope will probably sit at about half supply voltage (120v in the UK) due to the stray capacitance in the mains transformer etc. This 120v will have a high impedance and is most unlikely to cause harm to any healthy person.
However, one of the big concerns in the industry is ESD, Electro Static Discharge. With the smaller structures within integrated circuits, it is possible to electrically overstress the components and damage them, due to static build up on personnel, general items in the work area, and things like un-earthed soldering irons and test equipment. 120v from the un-earthed scope can easily zap CMOS ICs.
Is there any emphasis placed on ESD precautions in the consumer electronics repair industry?
Electrical Distribution Systems
The high voltage systems are three phase, and a neutral is not required, in a balanced three phase system, the neutral current should be zero.
At the local distribution level, from the local transformer, there are three phase conductors and a neutral conductor. The neutral is earthed, I believe near to the transformer.
Businesses that need a higher power will be connected to the three phases and neutral, a domestic user will be connected to one of the phases and neutral.
I have seen local distribution systems which use just one wire!
The return is done via the earth.
This was in Iceland, have a look at the attached picture, this is the power feed to a clifftop lighthouse at Dyrholaey on the south coast.
Curious stuff, I wonder what the load regulation is like?
JimB