White's removal at common in TMT all carries a tax. Grounded for Life wants the target tapped to come down cheaply, and Dimensional Exile is an aura that costs three and stays vulnerable to anything that peels enchantments off a creature. A 3/2 for three with a Banisher Priest enter trigger is the cleanest on-curve answer white has, and it walks straight into the 2/3s that anchor the format's common slot. The catch white drafters need to internalize: the base-mode exile lasts only as long as the kunoichi sits on the battlefield. Trade her in combat and she leaves, which immediately hands the exiled creature back. The body is the thing you are protecting, not just a clock. P1P3 to P1P5 in any white deck, P1P2 out of a thin pack.
WB Ninjas is where the sneak cost stops being a flavor line. That deck already runs the black mana and the unblocked-attacker density to set up the bounce-and-recast, and because the sneak version enters tapped and attacking, the enter trigger clears a blocker before combat damage rather than after. The exile then sticks even if the kunoichi dies later. RW Equipment never pays that cost: a suited-up attacker has no reason to bounce off the board mid-combat. RW takes this as a 3/2 with an on-enter exile and moves on; WB takes it as removal wired to its own attack step.
The medium speed of the format is what makes the sneak line live. You have the turns to land an unblocked attacker without racing a turn-four kill. The punisher is Stomped by the Foot aimed at the kunoichi: against black, killing her returns the exiled creature, which is precisely why the permanent sneak mode reads better than the base mode it shares a card with. Maindeck in any white deck, never the board.

