We'll need them because the robots left behind in the Hat-Lete are bound to put up some heavy resistance.
Yohko uses the robot left behind by Tanzer to enter the heart of Sakura Taurus, bringing along the rest of her friends, Lawson and Fluger.
Just the same way as future visitors of the Moon would understand that the mechanic robots and tools which they find there are left behind by creative humans many years ago... :).