I’ve met my fair share of people who stutter through therapy and self-help groups. Literally everyone who did the Del Ferro therapy reported the same thing: you’re fluent for the first few weeks after therapy but relapse hard after that, i.e., your stuttering gets as bad as before the therapy. And then they blame you for not practicing enough. And there’s no scientific evidence that the method is effective, therefore the public health insurance here in Germany doesn’t cover the therapy.