We are the advanced civilization that has built those hot baths. Being an advanced civilization, it's safe to assume that no single person knows all the knowledge necessary to build another hot bath, because it has long surpassed how much one person can learn in a lifetime.

But somehow there are multiple organizations that "know" how to build another hot bath, and newer and bigger baths are continuously being built all across the Empire.

And occasionally one of them stops working and thousands of citizens are angry, because they feel, being honest citizens of the Empire, they are entitled to enjoy these hot baths. Sometimes their very livelihood depends on the baths running.

Then the bath is fixed, and all is well again.