I suspect it's because in real life, you will have just sat through a death-by-powerpoint on principles of landnav for 90 minutes of some bored E6 reading off the slides to a whole bunch of even more bored E4's and then you get to play the game to practice.

Generally the expectation is that with a map, compass, and protractor a member of the Army should be able to navigate a land nav course(the simulation is very similar to the real courses). In practice, it's much more likely that a combat arms soldier would know how to use this than someone that works in something like cyber operations.

In my time in the Infantry we spent a significant amount of time working on honing landnav skills, both theory, and practice.

*Edit* Also, there is already a manual for everything you do in the military.