A good father would have taught him such thing. It's very clear that the people closest to the protagonist just have no idea how important she is.
With that said it's rather refreshing that there ARE very important people who are keen on her, unlike in many other similar works.
Problem is it's kind of a who's a bigger idiot situation.
What I mean is who's a bigger idiot?
A, the guy who was completely failed at his job of protecting something super important because he was too stupid to understand how important it was.
B, the guy who trained A and put A in charge of guarding the super important thing and never checked that A was doing a good job even though he knew the thing was super important.
C, all the other guys who never checked in the thing even though again, they knew it was super important.