An ever-growing cardpool is a burden for game design and development. Without rotation, every new card design must be weighed against all previously printed cards, a problem that only gets worse with time. Additionally, developers and playtesters must consider an ever-widening pool of potential interactions. Design is forever constrained by the cards that came before.
In addition to the constraints an eternal cardpool creates for design and development, it also creates a burden for new players. If the entire cardpool is relevant, then new players face a daunting barrier to entry; without access to every card, they are at a disadvantage to players who have been building their collections longer.
Furthermore, attempting to sidestep both of these issues often leads to power creep: newer cards are made relevant for new players and exciting for old players by being simply better than older cards. Power creep is often the death of a game.
Rotation is a way to solve these issues by imposing an arbitrary competitive lifespan for cards. Rotating old cards frees design space, simplifies playtesting, and lowers the barrier to entry for new players, without introducing power creep. This is why our flagship Netrunner format, Standard, as well as the introductory format, Startup, both employ rotation.
However, if you dislike the idea of rotation, there are other formats, such as Eternal, where you can still use your old cards! And, of course, when you’re playing casually, you can use whatever cards you and your playgroup like.