What you're missing is the rocket equation. The less weight, the less fuel you need and the larger your payload. We should trust the decisions of these experienced engineers who are deeply familiar with the tradeoffs involved in spaceflight more than our own intuition.
Yup, the rocket equation is truly brutal. Anyone who thinks legs are superior to a tower hasn't played Kerbal Space Program--and remember that stock KSP is easy mode. You don't need anything like the mass ratio that Earth rockets need.
