Rightly so. I once had to review a paper from a guy who only had half a dozen publications that were all but identical. Whole pages were copied between the papers and it wasn't at all clear what the novel contribution of each paper was supposed to be.

You can publish the same result multiple times, but please reference the previous publication and explain exactly what has changed that warrants another paper.

Is your implication that self-plagiarism is or is not a serious problem?