It's true that items are unique to games. But if you want to allow some kind of trading, you will have to implement it yourself (next to programming, art, marketing, etc.). Linking this to crypto-tokens could have the benefit that you outsource the trading part. Your players "own" their items through crypto tokens, and can trade them on crypto exchanges.
You can implement it yourself in a centralised way of course. But the question is if you want to spend the resources on that.