This study is really neat because as the article says the consensus was always Central Asia for the birthplace of cannabis and now we learn that it is East Asia.
It's not just about feeling good (though that can be threat enough for some authorities -- dancing bans[1], for example).. Cannabis can have psychedelic effects at high doses, and has been used for religious and sacramental purposes (there has been speculation that cannabis was part of the anointing oil used in the bible, and perhaps in some of the biblical incenses used for religious purposes).
Secular and religious authorities have historically wanted to be in control of what people feel, believe, and think.. so when a plant can alter that or is believed to provide a direct route to communing with a diety or the spirit world instead of relying on the authorities to tell them what to believe or think, then it's easily seen as a threat.
In the US cannabis use was also associated with the counterculture, with the antiwar movement, and with anti-authoritarian sentiment, and with minorities.. all seen as threats to the establishment.
If they can't vote, they can't kick Nixon out of power
> according to the Law on Public Security Administration Punishments, marijuana smokers shall be detained for 10 to 15 days and fined a maximum of 2,000 yuan.
[1] https://en.wikipedia.org/wiki/Cannabis_in_China#Legal_status