Eastereggs are a simple way of getting sympathy (for the less geeky ones like 'tilt') and geek cred (for the geeky ones just like this). Probably, some engineer just built if for relaxation (or training with the code), so the cost of it is neglectible.

A huge part of the appeal of eastereggs is the discovery. Listing them would actually remove that.

It is basically the same as collections of jokes: the are just not as great as one of those jokes randomly being told to you one evening.