[Scoundreller]

I'd also guess that China and Russia are big enough that satellites would go unused a lot while flying over them.

While Iran isn't tiny (17th largest country), the satellites have several other territories nearby by that could use up the capacity that a no-Iran rule makes available.

[KeplerBoy]

The satellites fly over China and Russia either way. Starlink isn't geostationary, they're quite a few of them above you at any given time and place.