Originally Posted by YYC009

This ^

The Bagrooms can often be near or at capacity during peak times. So you don't want your bag being taken off the carousel to make room in the bagroom for more bags without a can or tub for the bag to go in. If it is too early, then it could get thrown onto the floor somewhere and forgotten about until the end of the night cleanup. At some airports, the bagrooms are also common use and the airline may not be allowed to have access to it until a certain time.