[She makes a face at that, sticking out her grey tongue in distaste.]
Ugh.
It would take a really long time to explain it right, but I'll give you a very short version.
The King and Queen both have powerful magic. The King uses his on the Battlefield, to fight the war. The Queen uses hers in the kingdom proper, to protect from interlopers. For... A few reasons, really, our lives aren't precious. If we can't lay our necks on the line for our people, we don't deserve to rule.