I wish there was a separate room category for daybeds because it's really frustrating trying to secure one of these rooms in BC CL. The best advice I was given was this:
The rooms with dormer balconies usually don't have a daybed because they won't fit in there. There are dormer balconies for every class of room, but CL rooms have the majority of them. That makes the CL rooms with the least amount of daybeds.
Now as far as the categories of the CL rooms, my understanding has always been that there are not many GV CL rooms and most (all?) of those rooms do not have a daybed. Same with the Water/Lagoon view CL rooms. So when staying CL at BC, I always book the Standard view CL room because my understanding has always been that's my best chance to get a daybed. I will say most of my trips I've gotten my request. We did have one trip from recent memory where we didn't get the daybed and they brought us a cot.