Bitcoin's blockchain is absurdly expensive to record data on. It's much better suited to only proving data existed by a certain date by recording its hash value

Bitcoin's blockchain is absurdly expensive to record data on. It's much better suited to only proving data existed by a certain date by recording its hash value. There's also no real benefit to having the largest chain (designing a cryptocurrency specifically to build as large a blockchain as possible would be relatively trivial) or wasting computing power calculating endless streams of pseudo-random numbers. As for benefits of a private network: Privacy, while still being able to easily form consensus of records among all parties involved.