To answer this question I collected some data on past match history and ran the numbers
$138.49 Rare Secret Origin Forme Dialga VSTAR $1.25 Rare Holo V Origin Forme Dialga V $2.06 Rare Holo VSTAR Origin Forme Dialga VSTAR $18.20 Rare Rainbow Origin Forme Dialga VSTAR $12.42 Rare Secret Origin Forme Dialga VSTAR $3.69 Promo Origin Forme Dialga V $2.08 Promo Origin Forme Dialga VSTAR
that makes it so that they generally have an advantage over the opponent's monsters' ATKs, since those will be reduced while their own won't
They arent a way for Wizards to sneak a secondary banlist into the format, but rather a way for some long-established community norms around what cards dont belong at more casual tables to be more codified
However, it can also get the damage buff if your opponent is sniping the Bench with Moves that can target any of your Pokemon
In theory, theyd also work in a deck that cares about flickering creatures for maximum value, but the Ninja type makes their intended home clear