I'm currently reading "The Systems Model of Creativity; The Collected Works of Mihaly Csikszentmihalyi" and was really surprised at the rate of self-citation in the included papers. Now it does seem to me that the cited studies are relevant. And I can't judge whether there would have been papers from other authors even better suited for citing.
And why am I even reading that book? Well because of the persistence with which Csikszentmihalyi gets cited in other writings I read. How do I know these writers weren't shills for Csikszentmihalyi? I don't care all that much when the material is good.
So in the end should I care about backwater publications that cite themselves excessively? Because I don't have to read them. As a consumer I don't seem to get hurt by the practice.