Steve Bennett wrote:
It's not so much "inertia resisting the change" as "difficulty migrating content to Commons". We don't even discourage people from uploading free content to en.wikipedia. Buried in a whole page of daunting instructions on the upload page is a note that "if you are uploading a file under a free license (not fair use!), consider uploading it to the Wikimedia Commons". Another obstacle is that the descriptions of all the licences are totally different on Commons.
Many of en:'s habitual big uploaders have already switched to commons, so it's partly a question of how much we want to encourage smaller-scale uploaders that haven't made the move. It would be interesting to see the results of a query on who has uploaded the most free images to en: in the past year or so, and perhaps ask them their reasons for not using commons instead.
Stan