The bedroom in western culture is a retreat. To say it is “personal” space is wrong though. Access is the most private level of public. There is no social convention barring a guest from entering an empty bedroom. It is not the space that is private but what we do there. The barriers against the outside world are more mental.
So, as important as doors, as social barriers, are barriers to sound and light. The bedroom is where we change our faces, and the master bath has evolved to support this. So we keep our clothes here, to change our costumes.
Keeping our bedroom clean, our bed made—to those for whom this important—is a statement of psychological order, of readiness. Conversely, a messy room may indicate a statement of privacy from those who consider their bedroom off-limits.