Hong Kong’s fate was forever changed once the British Empire seized the island and surrounding lands after the Opium Wars in the mid 1800’s.
As the conflict’s name implies, the Opium Wars were largely fought over trade, money, and imperialism, and involved the British smuggling in opium to the Chinese public. Since then, the Chinese public's perception of drugs has been completely negative, blaming societal and domestic problems on drugs without any further critical thought.
Hong Kong has been no different; children are taught that all drugs are equally addictive and harmful to their bodies and to society, and if anyone were ever caught with drugs, they would face serious fines and consequences. Worst of all, they would bring shame to their families.
As it remains, Hong Kong has one of the most stringent penalties in the world for marijuana possession. If someone is caught with marijuana or other drugs, they can face up to HKD $1,000,000 (~ USD $129,000) in fines and up to 7 years of imprisonment. Of course, the maximum penalty is almost never enforced. The Hong Kong Police are more interested in catching drug traffickers and smugglers than individual users.
Nonetheless, you never know how the police will react if they find marijuana on you. Search-and-frisk is very common in Hong Kong, so carrying marijuana does involve some amount of risk. The Hong Kong Police generally profile young men that fit the stereotypical image of Triads and other gangs, as they will have a higher chance of being randomly searched.
Medicinal uses of marijuana aren't recognized by the Hong Kong government, and it's viewed as a “highly dangerous” and “highly addictive” substance. Occasionally, you may see government-sponsored ads detailing how dangerous marijuana is. The propaganda against marijuana today is so strong that you can draw an obvious conclusion - marijuana is on the rise in Hong Kong, and the government is doing everything they can to put an end to it.