Musk says SpaceX knows what caused the latest rocket failure

You use rockets optimized to get from earth to the LEO station, to transfer between the two stations, then one to get to and from the Moon. Cheaper, and you keep long lived and potentially permanent assets up there, anything you loft to LEO is done at tremendous expense, course.

Two flies in the ointment for assets beyond LEO and not under a lot of lunar soil/rock:

Apollo was primarily a political stunt to convince the rest of the world our technology as good or better than the USSR's, who'd we'd let get out into space first to get them to establish the open skies principle that orbiting over someone else's territory wasn't spying (something they were insisting up to a week or month before Sputnik). Such assets were superfluous for the stunt, plus there was a very strong RFK/LBJ prejudice against any hint of military utility in NASA's space program.

That plus internal politics which allocated the initial catch-up job to a group which was only good at making truly impressive launch pad explosions put us on the back foot in terms of getting out into space, and the Soviets made a fairly serious effort to beat us to the moon, e.g. look up the N1 rocket.

Second, and seldom remembered is that the whole program was predicated a quiet Sun cycle, that's the determining reason I've read why the last two missions were canceled, the program had sufficient delays that it was getting into the danger zone, and Nixon wasn't about to kill an Apollo crew.

For some SF coverage of this, read Heinlein's Podkayne of Mars where during an interplanetary voyage all the passengers and crew had to huddle for a while into the small shielded space the craft had for such an event.