Whilst it was pretty obvious that the refusal was due to the fact that you were using drugs for gain, Kotaku Australia has received a response in regards to exactly why it was refused classification in Australia.
The report confirms that “Computer games will be refused classification if they include or contain ‘drug use related to incentives and rewards”.
“In one sequence, an NPC is viewed on the ground, convulsing owing to a reaction from taking a Joy pill, which has subsequently turned bad. After several NPCs encourage her to take Joy and she refuses, fearing that it will have an adverse effect, they beat her with steel pots and a shovel, until she is implicitly killed.
In another sequence, the player is seen in first-person view, entering a telephone box that contains three large pill dispensers, each holding a different flavoured Joy pill. The player consumes a Joy pill and a swarm of brightly-coloured butterflies appear as well as rainbows and coloured pathways on the ground, improving speed and visibility for the player.”