While there is certainly a lot of value in encrypting data, that is, in making it unintelligible (or at least that is the intention) to someone without the proper decipherment, usually a set of keys, another alternative is to hide data from an attacker.
In the past this meant sending messages in blank wax tablets, where the wax hid an actual written carved message in the wood tablet itself. Deramatus was thus able to warn the Greeks of the Persians military intentions.
Today, of course, similar steganographic tricks can be used (say, of a GIF that encodes not only an image, but an actual message). Yet purposefully (and effectively hiding) data servers, not giving the contents of a database by name, and so forth) does have some value. Hackers usually hit what is easier to hit –and yes, do not use ‘admin’ as the username.