If you're not using it for Double Thread, then at the very least, it's another dual type Pokemon that adds 60 more damage to Rainbow Force, and its pre-evolution, Joltik, has free retreat, so that's a nice bonus in and of itself
Other than being the most rare cards in the Duel Links game, people desire them because oftentimes your most important cards in your deck are going to be UR cards
Worth a heads up before playing
Knowing which to use when is central to defending well: block to soak chip damage, counter to win the combats that matter
[4] During gameplay, the player must defeat eight Club Masters, each with a different deck representing one of the game's elemental card types