The key thing to understand is that any specific satellite spends far more time over the ocean than over a dense city. So for each busy satellite you have 10 t

The key thing to understand is that any specific satellite spends far more time over the ocean than over a dense city. So for each busy satellite you have 10 to 100 others on the same orbit which are still cruising over the ocean. To maximize efficiency you want to have similar load wherever the satellite is.