While it would also be nice to have a Mark as Read option for students to confirm announcement access, we still wouldn't know who has accessed what unless we specifically search.
Content pages could be used as announcements for triggers to get people's attention--i.e. they can't move on until they read the page--but this is still individual by individual by individual.
A tally would be helpful in some instances, but basically we need to know the number of student accesses AND who those people were. This would allow tracking the effectiveness of announcements and would speed up our ability to contact student by other means.