Earth orbit to lunar orbit, sure.

But you could also also use them for other things. The engines are about twice as efficient as chemical rockets for solid core designs, and since the fuel is generally hydrogen and no oxidizer is needed, that simplifies refueling, and also means you can loft that much more fuel per launch, because hydrogen is the lightest element, all other things being equal.

But you could also use something like that for maintenance of geosynchronous satellites, something we simply don't do now. And for even higher missions. Imagine being able to service the Webb Space Telescope like we've done with the Hubble Space Telescope. Having a near-Earth tug capable of getting astronauts to the Moon and back would also allow missions like that.

I kind of get the impression that you're not really imagining the possibilities here. Kind of like looking at a Wright Flyer in 1904 and asking "What use is it?", not seeing that something like that just opens the door for further development and that the jobs will be attracted to the application.

Heh, kind of reminds me about how the "killer app" for personal computers back in the early 1980's was organizing your recipes.

In short, if you build it, creepy ghost players will emerge from the maize.