This is merely my forward opinion in the matter, but it is far from merely impulsive
If you manage to do so, Espeon will devolve all of your opponents Pokmon by one level, potentially knocking them out in the process if they have more damage counters than their new HP cap
So why in the world would someone pay $40 for something they KNOW costs the other person only $10
Green Dragon Ninja Can Negate 1 Spell or Trap card per turn (Hard Once per turn) and thus makes a good pair with Mitsu the Insect Ninja, who can negate 1 Monster Effect per turn, or with Rank 2 Ninja Shadow Mosquito, who can the Negate the effects of Monsters which have Hallucination Counters, And Lastly, Paired up with Blue Dragon Ninja, who can also Negate 1 Monster Effect per turn
Yes, there are a few outliers like Kaito, Bane of Nightmares and Jace, the Perfected Mind
Simply put, it's the most efficient solution to deal with that particular color