I hear this a lot, but it really makes no sense to me.

An in-game item is really only suited for the game in which it exists. What good is a CoD FN FAL with certain balance, certain damage, certain bullet velocity, certain balance - in Minecraft? Anywhere else really?

Game creators go to extreme lengths to make their games balanced and fun and engaging. Opening up the ability for people to port in legendary weapons from unrelated games seems like the last thing game creators would want, and certainly, it's the last thing I'd want as a player.

Am I missing something? What's the draw?

Then if there's only one source for items, and only one place to use those items, you've got what we call a centralized system. Why would the game creator then want to give away the revenue from such a marketplace to "the blockchain" when they can just do it themselves and have a far more lucrative business model?