The rune gives people a special weapon that's effective against the magic beasts, because normal weapons aren't effective. Before even undergoing the baptism that gives people a rune, Inglis tests out that the ether control is enough to coat a weapon (I'm guessing) and deal damage to them. So when the baptism happens, a rune does not appear since it's not needed, as modern people don't have the kind of ether control Inglis has, as the rune weapons are a supplement to let them deal with beasts. People without a rune can only be basic low-ranking foot-soldiers, but that's fine with Inglis since they want to be on the front-lines all the time anyways.
