Ceiling decorations

Most ceilings are sparsely decorated, with the rare exception of spaces that are meant to leave an impression of grandeur (e.g. religious sanctuaries and lobbies in important government buildings). Typically, they're nondescript, painted in a solid color. And, people comment when rafters are left exposed because it's relatively uncommon. Why has this become the norm? Is it that most people never bother looking up?

We're certainly aware of how high ceilings are. If they're too low, we feel claustrophobic, and if they're too high, we lose any sense of intimacy. Children often want to put glow in the dark stars on their bedroom ceilings. So, why don't adults have a similar desire to leave their personal mark on the ceiling. It'd be easy to install convex tiles on the ceiling to create the illusion of stars twinkling in the night.