No volume for it in keyword planner or other paid services, censorship ?

If they don't sell ads on it they may not choose to show it.

They gain nothing in recommending those types of keywords to advertise on through anything a journalist can access.

They've already been fined hundreds of millions for selling ads for illegal steroids a half-decade ago.
https://www.wired.com/2013/05/google-pharma-whitaker-sting/

And they've garnered negative attention for selling ads to shady drug recovery lead gen services.
https://www.nytimes.com/2017/09/14/business/google-addiction-treatment-ads.html
https://techcrunch.com/2018/01/07/google-cancels-uk-ads-from-shady-rehab-clinic-referrers-already-banned-in-us/
https://techcrunch.com/2018/01/12/google-temporarily-bans-addiction-center-ads-globally-following-exposure-of-seedy-referral-deals/
https://www.reuters.com/article/us-alphabet-google-ads-exclusive/exclusive-google-unveils-vetting-process-for-drug-rehab-ads-idUSKBN1HN28X

Once they get that negative coverage they keep getting more of it even if they kill off their associated revenue stream
https://www.theverge.com/2018/5/11/17346788/rehab-marketer-google-ban-ads-uk-search-results

Blimey! Thanks Aaron.