Assuming you mean a digital game, as opposed to physical, the problem with users trading cards is that there is no money in it for the company running the infrastructure. If two users trade cards, then both got something they wanted but the company hosting the infrastructure didn't get anything. It's much more profitable for the whole thing to be linked to micro-transactions which allow players to endlessly gamble on getting the cards they want. Every time a player buys a pack/lootbox/pull of the one-armed bandit handle, the company makes some amount of money. The user gets their gambling dopamine hit and maybe a card they want. The lure of monetization is going to be too great for most companies to resist. So, it's all about the gambling mechanics.

Even table-top CCGs face this pressure. It's just impossible for the companies to control. So instead, they ratchet up the power level of cards with each new edition to force some segment of the player base to pay large sums of money to get the most desirable cards in circulation. Once enough of the desirable cards enter circulation, players can shift to just trading for or buying the cards they want outright and the company making the CCG is cut off from further profit. This is why new editions, expansions, seasons or whatever they are called are introduced on a regular basis. The goal of the game is to make the company more money by getting people to pay for cards which cost next to nothing to produce. But hey, if this is your form of fun, you do you.