If it's a robot, why can't it have 10 lockers, and the right one pops open when it arrives to your place?

On average that's only moving 5 orders maybe a pound or three each around with a 4000+lb vehicle. Still terribly inefficient considering how much of the energy being spent is simply to move the vehicle vs achieving work.

The longer the route, the harder it is for the food to stay fresh and warm/cold/frozen. It's a trade-off between efficiency, price, and customer satisfaction.