You can't think of anything? There's a half dozen use-cases that immediately come to mind that aren't possible without a blockchain.

One obvious use case is collectible items for games. People spend thousands on games like Hearthstone or Clash Royale. Imagine if the cards you collected in such a game were ERC20 tokens. Instead of all that value being locked up within Blizzard or Supercell's servers, you could freely trade or sell your in-game items. I think that would encourage players to spend even more money on these types of games, and could open up huge new marketplaces for digital goods.