Beside giving a good sense of what societies are like so you get a built-in detector for need to research, it can also provide facts along the way. Like, say, succession.
Wrestling with the political implications of having the monsters attack -- at the command of an intriguer, though that's not yet revealed. Toyed with the possibility that a nobleman will revolt on the grounds that the law requires that the king be a paladin, in which case he would have their legendary powers to deal with the monsters. Of course, that raises the question of whether he's a paladin himself. . . .
Then I remember the Russian Imperial succession, which is semi-Salic. Women were not absolutely barred from the throne, but one would only on the extinction of all male dynasts. Yet, at the moment, some claim the rightful heir is a woman. This is because the laws also required that the heir be born of an equal match, to a bride (or bridegroom) of a sovereign or royal house, a difficult condition to fulfill while not actually occupying the throne.
The order of "paladins" having grown so lax that only one man proved to have the powers at need, a woman could easily claim the throne. Well, put in a claim. I may even let her win. (And the nobleman will revolve, too. Perhaps two: one who's ready to brazen the claim out, and another who thinks the only virtue they failed in was courage, so he would succeed.)
Useful thing to have handy.