Pokémon is supposed to have a MMO-like market and free trade aspect to it where you can barter and haggle with things like shiny status, desirable IVs, version exclusivity, general rarity, even some items like Master Balls or Bottle Caps and more. This also led to other social features such as sharing Friend Safaris in the quest to obtain good Pokémon. It could be as big a part of the social aspect of the game as battling other players. It was once.

Now it is effectively dead because injecting means nothing has value and content such as Friend Safari has lost its incentivization. There's no economy in Pokémon because injecting exists. Everyone can print their own money. The only people who "trade" are 6 year olds who put up Bidoof on the GTS and ask for Mewtwo in return.