No, commercial quality T-1 access is significantly more than what you have at home.

The airlines had leased line access to join their local networks long before the internet was commericalized, and I wouldn't be so glib about assuming that they already have high-speed internet access ready for the taking. They probably have a private legacy network, with some access to the internet tacked on recently. They would rather the general public be on a completely separate system, and I guarantee you that DSL/Cable modem access isn't available at the airport, we have a hard enough time getting it in industrial parks at my company.

They are spending $900 per month or more for the dedicated T-1 line, and you're also too quick to dismiss the tech support issue.
A modem is a fairly straightforward thing, but the various proxy servers, settings, DNS addresses, etc. in a WLAN connection can be more complicated for hundreds of people to drop on and off the network each day. I have had to use tech support at a Hyatt with "free" access before to get connected, as every network is a little different.

Also, if it were free, they would need a lot more than 1 T-1.

All-in-all, I see why they don't just eat this