Everybody understands “Out of sight, out of mind.” If we put something away when it’s not in use, it preserves our attention. If we keep the object in a drawer, it’ll be more available than in the attic, but it still won’t cost any attention. If availability matters more than the cost, we keep it visible. And we organize more for visitors because the messes we’ve adjusted to would repulse them.

Progressive disclosure is software jargon for the same idea. We display just the most necessary things. That makes new users comfortable because their attention can handle that much. We keep everything else out of sight but available, so users can get more involved when they’re good and ready.