Prevent thefts of digital goods (like currency etc.), not theft of real goods. The blockchain does not secure anything in the real world, it just makes the difference (whether a good has been stolen or faked) more transparently visible. You still need real-world mechanisms to actually secure the goods.
Like in the popular example of a blockchain-based land registry: This registry would prevent corrupt officials from falsifying the records about which land belongs to whom, but they won't help you if there's a person with a gun on your land chasing you away.