[Scoundreller]

Some of it has to do with combustion breakdown products. Some Canadian producers got nailed with using (directly or indirectly) antifungals with that issue:

https://www.canada.ca/en/health-canada/news/2017/03/clarific...

[llamaimperative]

Some of it has to do with highly effective lobbying by food manufacturers and a highly restrictive approach toward cannabis cultivation.