I guess the designers figured the cargo does not need to get out from the inside.
Door locks and unlocks with a key just fine......
I've sure been hosed by my 81 B250 Dodge conversion quite a few times when the rear door's blown shut or my Son's reached in for a tool and shut the doors out of habit. A few weeks ago I had to call him on my cell phone to get me back out! That was embarrassing.
I've cut the lock mechanism out of a donor van to cure this situation sometime, probably when I pull the doors to paint them. The odd thing is that my 79 B100 had the interior handle and plunger of the same type as the side cargo doors. Must have been an option?