alt Hacker Newspolar orbits are hard, you have to take a big oblique track dipping into the lower lattitudes to run a trajectory that allows you to counter gravity.
the anti collision manuevers are hard as well.
orbits are simpler at lower lattitudes where you run a trajectory, close to parallel to the equator.
Populations are also far lower than at lower latitudes.
This affects both commercial potential (fewer possible subscribers) and bandwidth congestion (dittos). For both you'd want fewer birds in those orbits, and orbital dynamics only strengthen the argument.