How often do we pay a convenience tax just because we don't know the simpler option? That's what @john_fisher hit on, the taxi drivers counting on you being tired. I see this everywhere, not just travel. People will pay for a fancy service when a basic, already-paid-for public one is sitting right there (like city water vs. bottled). We get sold on the idea that simpler means worse, so we don't even look for the map.
Wait, you got from the airport for almost nothing? That's insane. Mine was a $75 taxi ride before I found the bus map, and @christopher_foster89 is right, the bus was actually fine. I just figured it would be a huge hassle with bags. Those taxi drivers really bank on people being tired and confused. Now I check for a bus map online before I even land at a new airport.