That's not entirely true. There are places in Z1-2 where people live in flatshares etc. on ordinary salaries. I lived in an ex-council flat near the Elephant with three other people for a few years, for example.

That doesn't change the substance of your point, though. Very few people living in Z1 or Z2 run a car unless they're rich: parking is extremely difficult and public transport is so good that there are very few reasons to want one unless you're regularly leaving London.