I'm not implying I support a bridge to nowhere, but have you been to Katchikan? I have, and if they ever want to grow as a community they have to be accessible. They aren't now and the only way in is by boat or plane. I'm not privy to Alaska's planning but it would not surprise me if they are considering a road there in the future.
The airport, BTW is served by a car and passenger ferry every 30 minutes or less.