Starship Super Heavy Ideas

Why doesn't SpaceX's Starship Super Heavy deploy a 1 meter wide metal flap that goes around the whole rocket that replaces the grid fins, and is in 4 distinct segments? This would create enough drag to significantly slow down the booster without propellant use, would give 'steering' capabilities and when not in use, would be flush with the body of the rocket.

All SpaceX would have to develop, is strong motors and rigid hinges, and they would unlock 10x more capability and the booster would look more sleek.

The image is AI, visualising my idea, it was not my own work, but i hope it helps you understand.

If image is too washed out: https://imgur.com/a/vbGQETL