At the Build developer conference last week it became a little more clear why Microsoft is not allowing self publishing of games for Xbox One.
http://www.gamesindustry.biz/articles/2013-07-01-xbox-one-devs-can-get-a-head-start-with-windows-8
By the sound of things the idea is to get indies to publish Windows 8/RT apps first (Windows Phone too if they are nice). They will most likely provide an SDK which will allow for those apps to be published on Xbox One app store as well with minimal to no effort.
Windows 8/RT/Phone devices have Xbox Live gaming hubs and by getting the indie devs to code 1 game for all Microsoft platforms at once, they are able to provide support for all of their platforms with minimal dev efforts, and maximize the app reach for the indie developers. Its a way to compete with iOS and Android which also allow for apps to be created for different platforms in one swoop.
Essentially they want to eliminate this:
Indie game developer -> Xbox One game
and instead have developers do this:
Indie game developer -> Windows 8/RT/Phone Xbox Game -> Xbox One Game
