It would take a lot more than just robotics to do the job of a courier. It would require next level A.I. to leave the station with a truck of packages and deal with all the on road issues one comes across. The robot would also need to be able to arrive at a stop with a blocked dock, make the decision to come back later, go to the next stop, oops it’s a bad suite number, go to the directory in the hallway and find the right suite, oh crap security requires deliveries to use the freight elevator, go find that, make the delivery, now return to the previous stop and get in a dock, but wait, they also have a pickup they want you to take and they don’t have an airbill, go back to the truck get an airbill and talk them through the process only for them to realize they want to send it Ground lol. It’s just not gonna happen dude...