Negative Earth V Positive Earth

[Cuppa]

No expert at all but the major oil pipelines I've been on all have 'cathodic' protection sites situated regularly along the main lines. I was told this was to help prevent corrosion of the pipeline.

Not my field of expertise though. Where's @Cuppa?

A little birdie tells me you know exactly where I am! Hope you had an enjoyable time out west. I actually went looking on the ‘net for the answer to this question about why cars changed to negative earth. In a nutshell I could find no agreement, only several different reasons repeated many times.
The cathodic protection thing which I reckon is a bit suss, something to do with a change to alternators with internal diode control which sounded possible even though I didn’t fully understand it, ��, and also suggestions that it was somehow cheaper for the manufacturers... which I also didn’t quite get. Another possibility was the introduction of radios into cars - perhaps anyone who knows a thing or two about radios might comment?