Reasons not to build a transporter. 1. You need a lander for mars so now you are building a lander and a transporter and sending both. Remember the lander will take many months to refuel on mars. 2.Starship has everything you want from a transporter vacuum engines, tanks for storage, cargo space and living space. Starship has everything you want in a lander same stuff plus legs heat shield and flight surfaces. With a separate lander your now carrying two of everything SpaceX wants to land a colony not an Apollo style mission a small lander won’t cut it. 3. You need to develop and launch a whole new vehicle which if it can’t fit into a starship payload bay must be assembled in space requiring astronaut man hours. 3. A new vehicle increases cost and bespoke component numbers. 4. A new vehicle requires development time and it’s own production line. 5. Requirement to lift cargo to the transporter move it onto the transporter then at mars off load it to a lander 6. More complex system leaves more points of failure, you now have two vehicles twice as many potential failure points twice as many backups required.