The title is reflective of the article itself, which uses data to show that the wealth of an NYC neighborhood’s inhabitants is on average directly correlated with the extent to which those inhabitants left during the last few months.

Alternatively the article could have “just” listed the boroughs as you suggest, but this would raise the question of why some boroughs emptied out and not others (also why there is visible clustering within those boroughs’ neighborhoods). This is the question the article tries to address.