There's only few people who can handle Cycles code well, their time is spent mostly on keeping the system stable and well supported. New developers are being introduced now, but there's always need for more people here.
Another issue is priority & focus... Cycles main target is to be a "production rendering" environment. Rendering with baked lighting is not commonly regarded as a good workflow, for that development time can be better spent on advanced optimizing (caches etc). The main use case is for making light maps for game environments, which is very relevant but not on the first priority list for the current core devs.