All markets are finite. But you're thinking too finitely -- remember that there was a proposal to use Starship (BFS?) as a point-to-point method of people transport too (London to Sydney in under 50 minutes I seem to remember).

You also have other services: Starlink is an obvious one they're pursuing now, but there's many other things that they could branch into with no effective competition right now, from harvesting resources such as Helium-3 to Rare Earths (ironic name), to... (thinks for several minutes) banishing people to the Phantom Zone?

But you get what I mean, it's not just about rockets, it's about the things cheap and reliable rocketry enables.