This has been asked many, many times. Im surprised no one has mentioned pretty much the biggest reason. They are figuring out vertical landings so that when th

This has been asked many, many times. Im surprised no one has mentioned pretty much the biggest reason. They are figuring out vertical landings so that when they go to other planets they can land, possibly refuel, and take back off without having to get the rocket back upright. There also aren't seas on Mars to gently splash the rocket down on. :)