Probably so that you wouldn't create immortal sims who never leave their businesses and end up living on community lots. Had they simply had a check in/out counter so we could have hotels, that would have fixed the problem. Then if there is a check/out desk the community lot would allow sleeping, and otherwise it wouldn't. Oh well...
With the 'aging off" and "maxMotives" cheat, we already can have immortal sims if we choose.