I didn't say a word about drones, if by drones, you mean quadcopters and the like.
As for robots, your thinking is too constrained. There are lots of design options that will handle snow just fine (and every other kind of terrain) that don't involve tires. Spider legs, for instance.
Vandalism: easily vandalized robots are counter indicated, obviously. Likewise robots that don't record what's happening to them. These are trivial engineering issues in the sense that solutions are readily available. They're no significant impediment to robot deliveries.
Fraud: One obvious solution is payment before delivery. Another, for payment on-site, is the same tech, or related tech, to that which lets a soda machine know you actually fed it dollar bills, before allowing access to the cargo. This isn't even a problem requiring solution before proceeding -- otherwise there would be no delivery now, and that's obviously not the case.
The only tech that really needs to happen that we don't quite have yet is the smarts to run the robot, and we're a little short on power systems, too. But we're very, very close. Solve those, get the cost down to where it needs to be, integrate available tech, and done.