I'm kind of new to the LCG world. I used to play/still play the Star Wars CCG, which stopped being created in 2001. Even though it's a dead game, there is still a relatively large player base. Naturally, this means that people still buy/sell/trade cards. To me, it makes sense: cards carry rarity, because they aren't being made anymore, etc.
So how does this work in an LCG? Is rarity even a valid characteristic of a card?