Crime

How about it's never actually been proven to work, and it's primarily been used as a form of torture for LGBTQA+ people. Every study of the subject included either willing volunteers, a sample already predisposed towards ensuring its effectiveness, or gay men at a time and place where it was a crime to be gay.

Consider for a moment the scientific rigor and motivationa for doctors involved in such experiments. Medical researchers, educated in statistics, make obvious mistakes in research design and then reach conclusions that are unsupported by math. If it isn't motivated by homophobia, then sadism seems to be the next most plausible explanation.