Let's have a look at two intriguing aspects of cards as a format: Orientation and Secrecy.
Consider this. A piece in chess can't change its function throughout the game because of its inherent physical limitations. No matter how much you turn that knight on its axis, it will always have the same characteristics within the framework of the game, and don't even think of turning it sideways if you want to keep it upright. This doesn't mean that its relative value can't change during a match, however, but it's impossible to note any change of status on the unit it represents. Is it wounded? Faster? Flying? Scared? Busy? Attacking? Defending? Granted, there's no room in the context of chess for any of these details, but there are other confrontation games that do have this additional depth and face the same problem. Wargames involving miniatures come to mind (please keep in mind that my knowledge of wargames is merely superficial and I'm trying to consider the genre in very, very broad strokes).
It's true that miniatures can change orientation to determine, for instance, if an enemy unit is in its line of sight. But how could one indicate status changes? Basic miniatures just can't, although there are always clever solutions to this (Heroclix, I'm looking at you!). These solutions are probably more costly and they don't seem inherent to the medium. So what's the great advantage for cards?
Cards are blessed with two interesting features – they have two sides (front and back) as well as a rectangular shape (well, at least the most commonly seen cards do!). The rectangular shape allows for 4 distinct orientations, which in a tremendous display of imagination we'll call straight, sideways to the right, upside down and sideways to the left. A chess pawn would be jealous of such flexibility!
Many games use these orientations to indicate different statuses. In Magic: The Gathering, a tilted card is considered tapped and thus unusable temporarily. The Pokémon: TCG is one of the few games that use all four orientations to indicate different lingering effects on the beasties. The Call of Cthulhu card game takes this one step farther -- exhausted characters are tilted sideways, but more interestingly, characters can also go insane. To reflect this, the rules instruct players to flip the card over. There are still other games use flipping cards to good effect. Yu-Gi-Oh has traps and defenders, agents in Arcana agents can be played facedown to hide their stats and Warhammer: Invasion has developments, just to name a few.
For simplicity's sake, most games that bother to include card orientation as a gameplay feature use only two positions. But due to the nature of cards, there's no one stopping a designer from using all four orientations -- eight if we include the variations resulting from flipping cards over. Naturally, the game would have to be designed with this in mind, but having access to eight different potential status from the get-go is nothing to sneeze at.
The fact that cards have a back is actually impactful for another reason. It allows players to withhold information from their opponent's sight and leads to all kinds of mind games, bluffs and psychological plays. This is considerably harder to pull off in other confrontation-oriented games that don't use cards. As a bonus, secrecy makes things more interesting even in cooperative games. Arguably, Pandemic would be a very different game if the cards held by players were public knowledge.
Open information is of course perfectly fine in many games, but cards allow designers to include secrecy if they so desire. There are, of course, numerous card-driven games in which all information is shared among players, although mainly in the co-op genre for obvious reasons. Elder Sign comes to mind (even if its categorization as card-driven game may be questionable for some).
It must also be noted that at some points throughout a game, the information in the cards is not only a secret for the opponent, but also for the player. Card-driven games usually employ one or more decks from which players draw. Even though you may have fine-tuned your deck and are perfectly aware of which cards are in it, you can't know for certain which cards fate will deal you on your next turn. I believe this tension is a very big selling point of deckbuilding games, and so it should be! It adds a layer of randomization without leaving everything to chance. But I would like to treat the topic of randomization in a future entry and I think I've said enough for today...
As always, don't hesitate to leave feedback of any kind and thanks a lot for reading!