Or, because they know that if DSP is done right, it can be a solution, but then make the incorrect leap that if it is done in DSP, then it's done right, which, at least with commercially available solutions, isn't always (or even usually) the case.
That said, I don't think it's fair to rule out DSP based on a few bad solutions, if good ones exist. I was just reading an article on all-band-pass filters that were designed to do exactly that -- correct phase.