To be sure, self-publishing is sometimes seen as a sign that an author believes in his or her work; for instance, photographer-turned-publisher Max Bondi said that “investing in a project shows that you believe in it”.
Nevertheless, part of the reason for the negative stigma is that many self-published books, particularly in past decades, were of dubious quality. For example, in 1995, a retired TV repairman self-published his autobiography in which he described how he had been stepped on by a horse when he was a boy, how he had been almost murdered by his stepfather when he was a young man in Mexico, and how his ex-wife had clawed his face with her fingernails.
The repairman spent $10,000 to have his 150-page masterpiece printed up, and, for promotion purposes, he sent copies to a local library, to the White House, and to everybody with the repairman’s same last name.
These efforts did not lead anywhere; today, the book is largely forgotten. —Wikipedia on ‘Self-Publishing’