Material in the Inbox is currently (as of 1.7.5) not included in context mode displays, whether or not it has a context or project assigned. The Inbox is intended as a place where you collect and prepare material for execution, not as a place to keep material while you work it. If you really want to do stuff directly from the Inbox, go look at the Inbox. If the stuff in the Inbox is so urgent that you don't have time to properly assign it to a project and context, why are you looking anywhere else for actions to do?
As always, if you have suggestions for improvements, use Help->Send Feedback or email
omnifocus@omnigroup.com to get them in front of the developers. It is possible to convince them that past decisions should be reconsidered, though sometimes after reconsideration, they make the same choice again :-)