[Note: this essay may give a negative impression on cards as a feature in videogames, but that is not the case]
Cards in physical card games are abstractions created for physical play where other more realistic means are not available or too expensive.
Video games with cards are themed around taking that abstraction and using them in an environment where more realistic interpretations of the what the cards represent would be available. In this context, “realistic” does not refer to whether or not the subject of the card is scientifically or biologically possible in real life, but how accurate it’s representation is compared to what it claims to be.
Instead of using a model (3d or 2d) of a soldier, such a game represents the soldier with a card, which in turn represents the soldier. The card will likely have an image of the soldier on it, which adds to the accuracy this representation, but is still far more abstract than a full 3d model, especially if it is animated. Such a model can be interpreted by the player as being the actual soldier in question, creating a basic level of immersion common in modern video games. This immersion is missing from physical card games because it is difficult to create a 3d model, but tabletop miniatures games do offer this. Miniatures games give more immersion than card games in this way, and video games give even more immersion but are generally expected to do so because of the relative ease with which they can do so. Since no one expects miniatures games to have animations or for them to move by themselves, their absence does not create a negative impression on immersion, whereas it might in a video game. Card and miniature games are seen as offering art that would normally not be available, and as such offer a level of immersion that was unavailable before card and video games.
However, since a video game is generally expected to have as much immersive representation as they are capable of, it is more noticeable when they do not. In the case of digital card games, it is strange for such a powerful medium to use the abstractions that physical games are limited to. In this case the digital game is limiting itself, but this is generally OK because it is done on purpose in order to recreate the experience of a physical card game. While legitimate, it is still strange to recreate such a limited medium that is doing its best to create an abstraction of a scenario. Instead of directly creating the environment that the card game is trying to represent, such games make an indirect and purposefully imperfect representation.
While this is not at all bad, it creates a dissonance between what the medium can fairly easily (and fairly commonly does) represent in a more realistic fashion, and what it choses to do instead. In a way, cards are usually no more than a rectangular and flat representation of something, but I think it is more accurate to
Some games like Hearthstone and Yugioh avoid this by making the cards part of the theme they are trying to represent. The player no longer sees the cards as abstractions, but as part of the world, and thus realistic. The player is then playing as a character using cards, instead of having to pretend that the cards represent something that they clearly are visually not.
Star Wars Battlefront, Commandos
However, games like Star Wars Battlefront use cards where they do not offer the experience of a physical card game and take the place of what could have been a more visual and immersive system. They are used to represent equipment carried by the player, and could be represented in a better way, such as the system used in the Commandos series. In Commandos, equipment in the UI is represented with each equipment item sticking out or on the backpack. This UI element (if taken alone) is immersive because it looks like what the characters would be carrying, instead of simply having a square button for each, or worse in my opinion, as cards in a deck. However it may be that some people prefer the card representation, or that they view this abstraction as a theme. Some games are themed to be even moe abstract, in which case they might not have any concern for realism in representation.
This all just comes down to how visuals are represented and personal preference. It may detract or add to a game, but is usually not a large enough issue to give a game a bad review. The only real effect of using abstract representations is that it creates a dissonance since you know that (usually) games can represent things more accurately or realistically. This dissonance could even be used to create a desired effect for the player.
The way a game represents things has a lot of potential to make a game’s environment and immersion.