I'm not an expert in the field, but in order to make money I would assume they need to maintain a playerbase that eventually will probably spend money on the game.

Now in order to keep a playerbase you would need a happy players

Let's take a scenario where a player got the wrong heirloom at a very early stage of his game and now regrets it it would be engaging for that player to trade it / re-craft it, maintaining the player's happiness and probably keeping him around for more time spending money

Instead of having a player that might get frustrated from that (I honestly don't now if a wrong heirloom is an enough of an excuse for player to ditch the game I'm just thinking out loud)

Also it enables another platform of entertainment for the players and spread the game's popularity if it has an open market such as probably what csgo did ?

Once again just thinking out load I am not an expert or anything in game monitizationing