I'm not sure you could design a ship's pool to accommodate 3000-6000 passengers.
I agree with most people that whether or not there is storage isn't the issue. If you wanted somewhere to put stuff where it wouldn't get wet, you could use a waterproof bag (
DCL even provides one as the CC gift right now). I think most people just want to reserve a chair to use all day long regardless of what they're doing right then. That won't be fixed by storage bins. I now wear a swim jacket and pants (no need for a separate cover-up to put somewhere and a zipped pocket to put my room card in) and swim shoes (no need to find somewhere to put my sandals). So I no longer need anywhere to put my stuff. Years ago, a storage cubby might have been useful, but I found my own workaround.