[Gud]

Not everyone takes the car. Why should people who don't deem it necessary to take a personal vehicle to one of the most expensive locations on the planet(city airport) subsidize those who do?

[kioleanu]

What exactly would be subsidized by the people taking the train if the people driving up to (not parking at!) the airport wouldn’t pay a fee?

[Gud]

The roads at the airport?

With that said, at Zürich airport, you do have ~5 minutes before there's a charge which I find reasonable.