TheMadBug

A big thing that people don't seem to be mentioning is this will restore a bit of predictability to your opponents moves.

Specifically, the more secrets (like a trap card I think?) are added to the game, the less chance you have of guessing or probing what the secret could be. This makes them all more powerful.

Likewise it's handy to keep in your head what each class could play for how much mana they have. If they left old cards in there forever it would be impossible for most players to keep track.