Atrios says: “Yes, most airports in this country have crappy transit connections much as most cities have crappy transit, but we do actually have some decent ones. Off the top of my head there’s Portland, Seattle, San Francisco, Chicago, Minneapolis, Baltimore, Philly, Washington (National), …”
I would add that America in some ways seems to be to do freakishly well on this score. Like Phoenix, Arizona is not really a mass transit town but it’s single light rail line offers very convenient access to the airport if you happen to want to go to someplace near a light rail stop. DART will get you to DFW Airport quite nicely but, again, your trip would need to be near a DART station on the other end. Which is all just to say that most American cities just don’t have much in the way of mass transit or transit-oriented development, but I don’t think there’s a particular problem of cities not remembering to connect their airports.