The surprise is that stations like Oxford Circus and those others
you've cited are not in the most busy group. To me, living in Leyton,
it's not surprising to learn that Wood Green, North Acton and Leyton
are three of the busiest. (The others listed are all interchange stations
which hugely increases the footfall).

Leyton Underground Station - and I have done the count several times -
has in the off-peak periods about 25 passengers every three minutes
coming onto the westbound platform with a similar number
alighting from trains in the opposite direction. In the peak periods
the numbers are much higher. (These figures are of course pre-Covid 19)

When I travel off-peak south of the river on National Rail services, I'm
always startled by how few people use the trains.