Why aren't Pluto, Ceres, Eris, Haumea and Makemake included in the base version of Orbiter?
Planetary textures are large - minor bodies which aren't seen much by the typical user aren't present, for the purpose of keeping the total size of the base package down.
They are however all, as others have said, available as addons.
Or it could have been as simple as the good doctor not wanting to bother.I think its mostly a case of finding a democratic solution to a complicated problem. We could theoretically have pretty much every known moon for the outer planets in the next orbiter release, a smattering of asteroids, and several dwarf planets, but as noted earlier, they arent really all that useful to have as mission targets.
They are constantly updating position and orientation. For a modern processor, it is not much of an issue, especially when compared Orbiter's other, more dramatic performance issues (D3D7, for crying out loud...) Performance really drops if planetarium mode is active, and planet markers are being drawn.Orbiter FPS also appears to suffer somewhat from having a lot of celestial bodies defined, not sure why that is sucking CPU at all if they're not being interacted with in any way.
I would like some expansion in the celestial bodies included with the next Orbiter version, but not too much. Some of the better known small-medium moons of Jupiter would be nice...