On Asgard and some culturally similar planets, magic is a masculine undertaking. Women are supposed to be physical combatants; enchanted objects are one thing, casting spells quite another. It's more acceptable for men to take up weapons than for women to fiddle with the arcane, and in either case it mostly just isn't. The queen has magic, but it's not sorcery - and she's the queen - so it's okay. Neither princess has ever been seriously accused of such unprincessly behavior as delving into the craft of seidr; they're both known to be fine warriors, each with a signature magical weapon.