How come some topics have descriptions, and others don't?

I mean those topics you can add in your profile of things you’re knowledgeable on, or interested by, wtv. Some of them, like movies, have little descriptions, but others don’t have anything. How is it decided what gets what? I know the staff does it yes, but how do you go about deciding what gets a description?
My guess is that some topics were chosen and created by staff, then they added descriptions to them, but the topics added by members remain empty of description. That’s understandable of course, would be a huge job describing every single one of them, (There must be like so many) and some of them might not be fit for description. Have the staff ever added descriptions to some member made topics? (That’s if I guessed right.) Do you ever plan to add descriptions to member topics?
Is it possible for members to send in suggested descriptions to topics that don’t have any?