In Trading Card Games (TCGs), there is a set pool of available cards to players (a "format") that are legal to play in a tournament match. New cards are designed by game designers and added periodically to the format at regular intervals. Occasionally, cards are removed from the format ("banned") for either being too powerful, creating gameplay which is not fun for players, or not functioning properly within the game's rule set. For the purposes of this debate, there are two versions of Trading Card Games.
In the "Magic: The Gathering" model of TCG, bans happen infrequently and the game designers generally choose to design new cards at a lower power level than previous ones so that they are not (usually) too powerful for the format. Older cards are generally more powerful than newer cards, with some exceptions.
In the "YuGiOh" model of TCG, the game designers purposefully design each set at a higher power level than the one previous to it, so that newer cards are often much more powerful than older cards. Cards are banned very frequently.