I also don't like using "football pitches" as an unit of size[0], but unfortunately you and me are not the target audience of this comparison.
> I guess around the world it's assumed that the reader has intimate familiarity with lining up sporting fields
Because it's probably true for the great majority of the population.
[0] - I've been to a real football pitch maybe 3 - 4 times in my life (for non-sports related events), I don't usually watch football and I don't plan on starting to do it. I'd much prefer for sizes to be measured in multiples of Space Shuttle wingspan, but I guess it won't fly with 99.9% of people ;).
> I guess around the world it's assumed that the reader has intimate familiarity with lining up sporting fields
Because it's probably true for the great majority of the population.
[0] - I've been to a real football pitch maybe 3 - 4 times in my life (for non-sports related events), I don't usually watch football and I don't plan on starting to do it. I'd much prefer for sizes to be measured in multiples of Space Shuttle wingspan, but I guess it won't fly with 99.9% of people ;).