They provide card advantage, late-game staying power, and flexibility for a wide variety of White and Black decks
Ultra Rare (/): These cards are less common than holo rares and often have unique artwork or features, such as full-art cards, EX/GX/V cards, and more
It's an excellent multiplayer mechanic because it allows for creature decks to avoid kingmaking scenarios, or purposefully engage with them in order to play politics or create periods for player interaction
This forced Red/Yellow players to trade with Blue who were getting an unfair bargain
Ishihara himself gave these cards to guests, who consisted of Pokemon employees
With Viridian Shaman type creatures you have to hold them back based on the game state to get any real value from them and with cards like Qasali Pridemage which can be more proactive you have to lose the dork in order to use it as removal