Well, the whole world did it, and the whole world failed, for fifty years. Just as it failed with alcohol, a much more dangerous drug than most. [0]
I'm not sure how Singapore fares, but Japan is also known for its hard-line drug policy. This just pushes the harm underground. Just because you don't see it, and society turns a blind eye to it, doesn't mean it's not there. tl;dr: the hardline policy towards drug use in Japan created a massive underground meth problem. [1]
[edit] It doesn't take much research to find out something quite similar is happening in Singapore, too.
> “People think drugs are very hard to get in Singapore, but actually before the pandemic they were everywhere, and even now there are people selling them.” [2]
Hardline policies don't reduce the harm. They just stop people from asking for help.
[0] https://www.economist.com/graphic-detail/2019/06/25/what-is-...
[1] https://www.vice.com/en/article/xg8q7k/how-stigma-created-ja...
[2] https://www.straitstimes.com/singapore/courts-crime/young-an...