Chat is people hanging around in a room.
Discussion is what is prompted by a question. However they're turfed into chat.
If the points discussed are worthwhile it seems worth keeping them tied with the question that prompted them.
Plus it allows one to go away and think about what is said and come back with a response - whereas chat is immediate.
Presumably SE pushes discussion into chat so that discussion doesn't clutter up the Question, but if discussions can be 'rolled up' I don't see why that should be a problem.
If the discussion is long, can one use 'data' techniques to trim out what looks like lo-value stuff; and perform other house-keeping devices?