Idaho, the guy in the video above explains it quite well. For a visual, look at this real-time map of where Starlink satellites are. You'll note how close together they are at the northern extreme of orbital path, and how far apart they are nearer to the equator. With fewer satellite "in view" from any point on the ground, the less reliable or possible coverage will be.
LINK (Zoom in and you'll see that this is a live display, every satellite shown is moving.)
StarLink isn't geosynchronous; they orbit at about 550 km. That's the whole point of Starlink. Geosync communications involve a significant latency or "lag" as the signals pass up and down, a lag too great for lots of uses.
