This is just an opinion, but I think not having as bad as a drug problem that the US has is a factor.
I go walking in various areas and often see druggies smoking the pipe or injecting. And this is right on the sidewalk in plain view. I've seen the same in Vegas as well. So these are the only 2 cities that i've personally XP'd. But Mrs. CMO says she often sees the same in Seattle, Portland, San Fran, San Diego, and San Jose.
I have friends in Japan who live in various areas and they don't see people using drugs on the street.
The first city I ever visited with a rampant, publicly visible homeless population was Washington, DC. That was when I was visiting my girlfriend and her parents in Maryland while we were in college (1982). I never saw this problem in NC no matter which city or town I traveled to. To see that happening in the capitol of one of the greatest and richest nations on Earth made me sad and angry. We send people into space. We cure diseases. But we can't find a way to get people living on the streets some help? Not just financial help, but solutions.
When you consider drug use and drug addiction were not uncommon in the 80s, I tend to think drugs and homelessness are symptoms of underlying conditions: mental illness, cost of health care, poverty, unemployment, education, social norms, etc. When you're hearing voices or clinically depressed, using drugs to escape the pain and torment looks attractive.
How many addicts are that way because they suffer from undiagnosed mental conditions -- conditions they choose to ease by self-medicating?
Our system supports and enables the homeless to continue to be homeless and to do what they do. While it's true nobody can clean up their lives until they want to do it, that doesn't mean we should make it easy or less embarrassing. Provide services, but expect something of value in return -- work at a shelter or food bank, clean up the trash around homeless camps, etc. Living on the backs of working Americans should be discouraged. instead, it's an accepted Liberal policy.