It seems to me that DCA might fare much better if people could buy a 2 day DL/DCA park hopper pass. I was trying to plan a tentative trip a few months ago (which didn't work out) and got frusterated. A three day ticket was the smallest number of park hopper days I could buy. I really wanted to see DCA but didn't want to have to spend a whole day there when it is only a half day park (or so I've heard numerous times). I also didn't want to buy a 3 day hopper when I would only use 2. I would have been more than happy to buy a 2 day park hopper and spend both days in both parks. I bet a lot of people run into this problem and decide to just spend one day at DL.
Look at it this way......I love AK in Florida (alot) but I don't usually spend a whole day in this park because it is new and has fewer attractions. If I didn't get park hoppers in WDW I might not be as inspired to go to this park and pay a fulls days admission here either.