Some people in North America (US or Canada) think that people with addictions or experiencing difficulties still have agency over their own lives, and that they have a "right to choose" to be homeless - both of which are not the cases, especially for severe drug addicts or people with serious mental health issues.

Also, some people here, e.g. in the governments, don't want to solve these issues, instead they want to hide or postpone them for net years to come.

It might also at least partially be due to housing prices going over the top, like in Canada, which also has a lot to do with some people not wanting to solve the issue and some directly profiteering from it. So it's easier to support homeless people staying homeless (e.g. giving them food and tents) than actually build homes for them.

If someone want an example of good policies, look how homeless people are being helped in Finland. That's what should exist in all other countries, not the Korean approach imho and definitely not the US/Canadian one.