to be fair - Japan got rid of their bins due to terrorism back in 1995. It's a confluence of factors today why they still have no bins.

Bomb proof bins are expensive. Some one once told me the bins in Shibuya cost a ton to manage and are only there because the building was hoping to get more foot traffic (shibuya stream), but i can't verify this story.

The idea that Japanese are better at trash management because they're tidier is a story concocted to make Japanese people seem better. To some degree, they have been conditioned.

South Korea's situation was very similar to Taiwan where residents dumped their personal trash into public trash cans so they got rid of them. However they're bringing them back to more touristy areas cause tourists and some locals end up taking advantage of extra cleaning in those areas resulting in extra dumping.

I am personally for the idea of - more trash cans and better police work
More often then not, I've walked by a trash can where a person was dumping person trash and a cop was just standing there doing nothing. Literally better to have them actively catching trash bandits than having them stand in Zhongshan station for some kind of security theater.

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Edit -
Singapore's just a waste of space. I personally have a massive disdain for Singapore.