Probably to find out how many people do stuff like type their username backwards as a password/what kind of patterns they use. If that is useful enough information to warrant publishing data like this is debatable, yes.
Also interesting, how features of a username might correlate with password strength. Who do you think uses a stronger password, someone with the username "carguy551978" or someone with the username "w1ntermute"?
carguy followed by the 24'th n such that 1 + n + n^13 is prime, followed by the 34'th such n? I would expect a very, very strong password from someone who picks their username like that.
