So why would an airport operator tarmac over valuable land except to earn an income from it? Barriers, ticket machines, cameras, trolley parks, security etc. all cost money as well as the tarmac. Airport operators are not charities you know. As it is, they have to make all this investment without any guarantee the airlines will ever turn up, or stick around for long before being seduced by some other airport.
If there's no return from developing the land as parking, why bother? Just concrete it and put planes on it instead.
"No car park? Sorry sir, no-one wanted to pay for it."
