I don't think it is so much the strange, almost glitch like color pallets sometimes produced, especially when the HSV shader did those "interesting" effects.
I think it's more of the fact that at the default intensity, the colors are so bright and contrasting (even when using a pallet you could conceivably see on planets) that it is a bit too distracting for a background object.
Again, IMO, the new planet graphics are great, but are turned up a little to bright and contrasting on the default settings.