Not the best example...

https://www.youtube.com/watch?v=EQQlREtqAM8

As far as I understand, first one Ocado robot went on fire, it doesn't have a sensor for fire so it kept going. Neither do its neighbours, who pass right by it and catch fire themselves. And so it keeps going until everything is on fire.

Price, depending on how far away you live.

Why even go to the airport? Take the train to where you are going.

I doubt the robots have sufficient enough traction/mobility to navigate on any surface that isn't reasonably smooth like tarmac. Also I'd wager the car park the robots go to isn't that far away from the drop off location, most likely on the same land owned by the airport.