For outside staterooms up to and including category 5, the steamer trunk fits into a recess in the wall. If you look at the deck plan, you'll see the most staterooms have one long wall that jogs in and out. This means that the steamer trunks in two adjacent rooms are effectively side-by-side, not back-to-back. Every inch has to count on a cruise ship.
However, some staterooms are up against straight bulkhead walls, so they don't have a recess for the steamer trunk. The steamer trunk can't go against a straight wall because there would not be enough room between the steamer trunk and the bed to open the steamer trunk or to walk between the steamer trunk and the bed.
That's why 5020 and 5520 don't have steamer trunks, but the other four SPRs do.
There are also other rooms in other categories that don't have steamer trunks.
DisCrazzy said:
We just sailed in room 5022 & 5024 last month. Both had steamer trunks, but they were smaller than the one in our cat 4 that we had in Aug. about half the size. Still had plenty of storage though.
The steamer trunks in the four SPR that have them are the same size as the steamer trunks in other outside staterooms up through category 5.
Category 4 does not rely on a recess in the wall because there's a little more room to work with. I did not realize that this also allows a larger steamer trunk, but that makes sense.