Right now, when you purchase Steem Monsters booster packs, you have no way to verify the code that is being run to choose the cards in your packs. You have to trust that @aggroed and myself are generating the packs in a fair and equitable manner, which means that this portion of the game is currently not decentralized.

And even then, decentralized computing has its own trust issues to deal with concerning random number generation. A trusted, centralized, RNG is actually a lot easier to deal with. Since the results of pack opening is on the ledger, we can monitor for hijinks like messing with drop rates or 'lucky' users.