This would add a level of control from the module to what is contained in them.
Having a lock on module availability is great but sometimes I would like to control when the contents of a module is seen. Availability dates for quizzes in modules is an obvious requirement. Why not have control for visibility of content pages?
Example: I have a "Study notes" module with a content page for every topic I lecture on. Each page contains study materials. I prefer not to let students see ALL materials at once so I have to remember to publish each content page when the time comes. Of course I forget once in a while. If I could set each of those pages to appear when needed, my worries would be over.