From what I followed, its because:
They already send payload to space with the falcon rockets (reliable cash cow) and
the only point of starship system is proof of concept of full reusability. There is no point to the whole project if they dont achieve this.
They are constrained in launches, either through regulatory (FCC) or engineering timeline
and so far, every launch counted. They achieved a substantial improvement.
If they dont catch the starship (upper stage), the whole project is pointless so its important keep things simple (details like payload door, cargo dont matter) until they achieved the whole loop (land & catch starship)
They already have a cheap way of launching. Cheap for current market rate. Whole point of this project is to improve cost by / 1000.
They achieved substantial progress with every flight.
1. It flies, 2. hot staging 3. reach orbit 4. land both & heat shield, 5. catch booster, 6. extreme conditions & improve heat shield.
If they dont catch the starship (upper stage), the whole project is pointless so its important keep things simple (details like payload door, cargo dont matter) until they achieved the whole loop (land & catch starship)
They already have a cheap way of launching. Cheap for current market rate. Whole point of this project is to improve cost by / 1000.
They achieved substantial progress with every flight. 1. It flies, 2. hot staging 3. reach orbit 4. land both & heat shield, 5. catch booster, 6. extreme conditions & improve heat shield.