It’s anonymous to a degree, although the blockchain itself is a record of every transaction.
For example, whenever a Bitcoin transaction is completed, it’s recorded on the blockchain. If someone has access to your public address, they can search for it to see how much you’ve sent and received in the past, as well as the public address of who it has been sent to.
Considering the above, it’s clear to see why the additional privacy provided by a VPN is worth it. Whether you’re using Bitcoin or an altcoin, security should be important to you.