Oh in this instance it's not about having a public record. It's about every transaction having a hash of the previous. Then it gets hard to forge old data without altering all records after the forgery. It's still possible but takes more work and can make the tampering easier to discover.

And for data loggers not connected to the internet this helps. It would be just as good to put it in a central repo if there was an internet connection available. But if you're logging a refrigerator temp on a container traveling between countries there isn't going to be a cheap option for internet.