Securing one entrance well is easier than moving along with revolving one. It is way simpler to stand still and aim with a gun than walk along shifting door way and aim a gun.
Serving food is simpler since you can just carry a cart with say a soup pot on one entrance and hand in bowls of it while the thing rotates. With moving door you'd have to keep moving the pot or pre-laddle the soup.
Same goes for all other housekeeping tasks. When the prisoners take their linen and clothes to wash they can not have any contact with other prisoners as they don't walk past their cells.
Bringing prisoners in is easier since they will always move along the same exact route no matter what since that is where the door is.
You could also potentially keep the prisoners from knowing who is in the same jail as them if you don't let them see one another. Obviously sound still carries, but some prisoners might not want to talk, so you could also consider it a privacy feature.
It also means you can firmly attach the bars to floor and ceiling making the cells more secure.
These are just off the top of my head, I'm sure there are others as well. While I can not think a single good reason why the bars should move.
Maybe because they are so much heavier. Prisoners would probably be able to make the door revolve much more easily. The cells, even if it is possible turn them with a hand crank from somewhere, wouldn't be movable from the opening by hand.
In Tom Scott's video, posted in another message in this thread, he notes that the inventor partnered with an iron foundry owner. Each set of cells is notated to be 30 tons of steel: more steel vs. would've been needed for a simple circle of bars that rotated.
Would the cells and prisoners actually be heavier? If you have a giant cage of iron bars, I imagine the interior structure, which just needs the walls between cells, and the floor, would be lighter actually.
Serving food is simpler since you can just carry a cart with say a soup pot on one entrance and hand in bowls of it while the thing rotates. With moving door you'd have to keep moving the pot or pre-laddle the soup.
Same goes for all other housekeeping tasks. When the prisoners take their linen and clothes to wash they can not have any contact with other prisoners as they don't walk past their cells.
Bringing prisoners in is easier since they will always move along the same exact route no matter what since that is where the door is.
You could also potentially keep the prisoners from knowing who is in the same jail as them if you don't let them see one another. Obviously sound still carries, but some prisoners might not want to talk, so you could also consider it a privacy feature.
It also means you can firmly attach the bars to floor and ceiling making the cells more secure.
These are just off the top of my head, I'm sure there are others as well. While I can not think a single good reason why the bars should move.