They're used to play Limited formats, like Booster Drafts, as well as to build a collection of cards for use in Constructed formats, like Standard
The obvious corollary is that theres going to be downward pressure on the basic versions of serialized cards, as the value in new sets is now spread out and skewed in favor of super-rare chase cards
The goal is to have some continuity between Gateways learn-to-play experience and the actual experience of playing Lorcana at a store, and its beautifully executed
This is a glaring loophole in the game and if left unchecked will mean the majority of top tier decks will simply run Dusknoir to gain advantages they otherwise wouldnt have access to
Its important to be able to distinguish whether or not your collectible Charizard cards are real or fake
Personally, I think this is a great idea, as in the past there have been criticisms that too many cards in a single set have been serialized