Weight. Legs weigh a lot. That's dead weight for a launch system, and it serves only to reduce payload to orbit. For Falcon 9 that's not that big a deal beca

Weight. Legs weigh a lot. That's dead weight for a launch system, and it serves only to reduce payload to orbit. For Falcon 9 that's not that big a deal because they're NOT trying to reuse the second stage. Whereas with Starship they need more fuel to recover the ship, and that means they need to save weight elsewhere to avoid losing too much payload to orbit.