Once again, we are talking about blockchain, not Bitcoin
You realize blockchain is used by many large companies for practical purposes, not just by hobbyists swapping magical internet money, right?
Many large retailers (e.g. Walmart) and pharmaceutical companies use managed blockchain solutions (e.g. IBMs supply chain software) to track end to end process flow and see the pedigree of products at their end destination, because it means the end user doesn't need to request unfettered access to 6 different companies ERP systems to know when the hell their purchase order is getting delivered
The poster above asked for a use case. I gave one.
Frankly I don't give a shit if the market penetration of said use case doesn't meet whatever arbitrary cutoff you have deemed sufficient for something to "exist" or not - the QR code on the back of every north american bag of Starbucks beans is proof enough. Whether its more or efficient than a traditional RDBMS is irrelevant