Lots of bad things are statistically unlikely to happen to you. Throughout your life, though, one or two of these *unlikely* events will happen. You can't just dismiss things because they're unlikely.
In the case where an offender is a stranger attacking a stranger in a public place, and it seems possible for him to repeat his offence, of course it makes sense to publicise some details. Of course if he repeats, there's a very low chance it will happen to YOU, but someone will become that unlucky 'statistic'.
By making it public, if anything, the offender may be deterred from doing it again. For the police, perhaps, they'd prefer he does it one more time so they have more chance of catching him. Is this the decision they're balancing? I hope not.