Responses
It could be, that without Lloyd’s modern knowledge, they were unable to maintain them over time. (Also we don’t know from The Prince That Sells Medicine whether the sewer systems are still intact, although the contract with the poop burning dragon should be over by then)
Honestly, now I'm confused. Why is the world at "The Prince sells medicine" (?) Still medieval? They aldy have fricking apartment buildings, missles, proper sewerage systems etc etc in Lyod's time , did they just gave up inventions?