This is JUST a guess but I wonder if one of the reasons EA is holding off showing the titles (Madden Wii U for example) is because they want to have the 2 tablets working with it when they show it off. Nintendo announced the Wii U would support 2 game pads but they didn't show any games with that capability, so maybe they only got it working recently. That might explain the delay in showing it.
Yep, and this is explained here where i revealed the 2 gamepad support one week before the conference
http://www.neogaf.com/forum/showthread.php?t=475981
Concretely, third-parties weren't aware that such a support will be possible until they received the mass production dev kits, roughly a month before E3. And yet, it wasn't activated, they were waiting for it, surely through a new SDK or something else (update, etc.). A new SDK was launched at the beginning of june, i don't know yet if it has unlocked the second DRC port on the dev kits, if it's the case, well, studios will have from june to launch to integrate it. If it's not, i hope it will soon to see titles using a second Gamepad not too far away from the system release.
But as explained and confirmed by Iwata in its twitter, it's likely all (or nearly all) the launch titles will focus on one Gamepad, for the reasons above.
Now we need to speculate on the workload, the development time, needed for EA, to implement a second gamepad, basically adding the team management interface of their next madden for example, on a second controller. It shouldn't be as easy as one could think, rendering a third-content will introduce another resource consumption, even small in case of an interactive map/player board/etc. and they will have to make sure the framerate on the main screen is satisfying, etc.