I think the other important use case is that sats without a ground station in view can backhaul traffic to another set of sats (for cruise ships or remote islands).
even just the ability to hop 1 satellite can greatly extend the range of one spacex earth station. right now, as the parent poster mentions, the moving LEO satellites need to be simultaneously in view of the CPE antenna and a spacex earth station.
and also relatively overhead of the CPE antenna, since the starlink customer terminal is a phased array that does dual beamforming in a 'cone' of view directly above it. just because a satellite is visible 5, 10 or 15 degrees above the horizon from the POV of the CPE doesn't mean it can talk to it. the system is definitely reliant upon a fairly high satellite density.
with the ability of the satellite that's generally overhead of a starlink earth station to talk to the satellites immediately behind, and preceding it in its orbital plane, and then those two additional satellites to talk to the CPEs underneath them, the possible coverage area can be greatly increased.
3D visualization of starlink orbits and coverage footprints:
I had a friend that worked at the south pole for a year. They had a few hours a day they could access their main communications satellite. Something like this could be a game change for remote research stations..
