Why cant they just admit weed causes Schizophrenia?

"Up to 50% of patients with cannabis-related psychotic symptoms presenting to the ED requiring hospitalization will go on to develop schizophrenia. "
https://www.frontiersin.org/articles/10.3389/fpsyt.2021.640222/full
"Cannabis is involved in approximately 50% of psychosis, schizophrenia, and schizophreniform psychosis cases"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3927252/
"In one recent study that followed nearly 2,000 teenagers as they Smoke rises from a marijuana cigarettebecame young adults, young people who smoked marijuana at least five times were twice as likely to have developed psychosis over the next 10 years as those who didn’t smoke pot."
"One of the best-known studies followed nearly 50,000 young Swedish soldiers for 15 years. Those who had smoked marijuana at least once were more than twice as likely to develop schizophrenia as those who had never smoked pot. The heaviest users (who said they used marijuana more than 50 times) were 6x as likely to develop schizophrenia as the nonsmokers."
https://www.health.harvard.edu/blog/teens-who-smoke-pot-at-risk-for-later-schizophrenia-psychosis-201103071676
"1/5th of cases of schizophrenia among young males might be prevented by averting [Cannabis Use Disorder]"
https://www.cambridge.org/core/journals/psychological-medicine/article/association-between-cannabis-use-disorder-and-schizophrenia-stronger-in-young-males-than-in-females/E1F8F0E09C6541CB8529A326C3641A68
Daily weed use was associated with increased odds of psychotic disorder compared with never users, increasing to nearly 5x increased odds for daily use of high-potency types of cannabis. The PAFs calculated indicated that if high-potency cannabis were no longer available, 12% of cases of first-episode psychosis could be prevented across the 11 sites, rising to 30% in London and 50% in Amsterdam
https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(19)30048-3/fulltext