Because the truth is that phrenology has never really been discredited. Granted people don’t typically go around measuring the bumps on people’s skulls any more, although who knows how the Quillette lads are currently planning to find genetically optimal brides. But when phrenology was first debunked, its foundational assumptions did not simply go away. Rather, they were dispersed across other disciplines. Actual bumpology might have been a scientific non-starter, but phrenology was nevertheless deeply influential on the development of modern anthropology, criminology, and evolutionary biology — as well as eugenics. The phrenological account of the mind continued to be influential, throughout the Victorian era, in popular psychiatry. It is in these assumptions that the contemporary heritage of phrenology consists.
From People keep trying to bring back phrenology by Tom Whyman