Right. And why so much unnecessary detail down to the quark level?
(Of course, if you really like the simulation idea, maybe we're in an unimportant corner of the simulation and the real action being observed is elsewhere. Much simulation-hypothesis blithering has the same human-centered problem as theology.)
(More promising was Wolfram's attempt to define physics in terms of cellular automata, which does not seem to have worked out.)
How do you know it's simulated in detail? It could be just in a sufficiently coarse level of detail and compute detailed events only when they are observed at that level. Quantum mechanics actually has some spooky things that would be explainable by "lazy" computation of the universe.
Maybe they're just the kind of game designer who obsesses over details, even if those appear superfluous to the core experience. Like say, the makers of Star Citizen. Or Dwarf Fortress.
After all, many games in our own world have far more detail in their world building than we'd ever normally see, often even including stuff that's outside the view of the camera or contingent on the player doing something they'd never normally think of doing.
Alternatively, it could be for future DLC purposes. Or lootbox type gambling mechanics not yet implemented. Or hell, just dummied out 'beta' content. For instance, the Legend of Zelda Breath of the Wild has every enemy killed instantly by the final boss' laser attack, despite the fact you're never going to encounter a single enemy in said battle. Why? Who knows, maybe it was planned at one point, or left in as a failsafe.
Same could apply to the 'real world' too.
But that's exactly how it is with our Universe! There's clear evidence that the important and relevant stuff happens only in the Solar System, and the rest of the Universe is just empty procedurally-generated useless filler.
I suppose it's possible that in some simulations "they" do leave the sky blank, in others they include randomly distributed stars, and in ours they've been grouped into galaxies. Perhaps if you were bored you'd try running it a few thousand times on each setting to see if it makes a difference?