Because the study pushes the narrative that correlation is causation, and that's just not true. The data is interesting, but the spin is irresponsible. Many people with mental health issues feel a stigma to seeing therapists and reach for something to numb the pain.

Plus, just because something has percieved negative effects on life outcome doesn't mean we outlaw it. For example, alcohol, prescription meds, having children before completing your education, the lottery, cigarettes, etc.