The reason is simplejust by returning a Pokemon card from your hand to your deck, you can search for any Pokemon card you want, making it a true game-changer
Reddit user u/Sability, for instance, noted how Esika being a cute to brute is an insane flavor fail, imo
"The cards have serial numbers, and no boxes are the same
But, of course, provided you're keeping two or more cards in your hand when on the receiving end of a discard spell, you should always take into account what kind of synergy or play style will emerge from keeping each set of cards
Basically, you can not only see the future, but also invest in it
Like most Pokmon cards, the value of Steelix depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Plasma Freeze)