The main cause is pretty simple. The police in San Francisco just do not bother them in certain neighborhoods. In most other cities police routinely pick up the homeless and dump them some place far.
So the absence of homeless is usually not a sign of better humanity, it is usually a sign of cruelty. This is especially the case in the US. There are other countries where they have better treatment for poverty and mental illness (most homeless are mentally ill to some extent) where the absence of homeless on the city streets may mean actual absence of homeless. But this is not the case in the US.
Thus, even if the sight of homeless in San Francisco is so terrible, one should keep in mind that San Francisco provides the best treatment for them in America.
I used to believe this based purely on having heard it all my life. But a friend of mine recently made an interesting point: he asked me what race homeless people are. My answer (at least here in LA) was that they're almost unanimously black or white. Never Asian. Never indian. Rarely Mexican.
I countered that it could be due to Asian and Mexican cultures being more culturally inclined to take care of their own, but I haven't fully convinced myself that that's the case.
My friend who made this point happens to be black, and his explanation was that having grown up in a black neighborhood, he noticed that black and white people have a sense of entitlement that other races don't often have, both for reasons that don't need explaining, and that that type of attitude begets unfortunate circumstances. I don't know whether I entirely agree with this point either, but it certainly makes you think.
It's very possible I'm off base here. I'm going purely on observation and anecdotal things. Do you happen to have any hard stats off hand?
Edit:
I looked it up. You're right in that Latinos hold the second highest percentage of homelessness at 33%, but when you consider population size, it sort of becomes irrelevant. Latinos make up 47% of the total population in LA. Blacks make up only 9% however they're a full 50% of the homeless population. This means that per capita, Latinos are 5 times less likely to be homeless than blacks.
The SF Chron (check the earlier links) distinguishes between "chronic homeless" and "hardcore homeless". Chronic homelessness appears to be more of an economic condition related to poverty. "Hardcore homelessness" is more severe condition, a permanent and very harsh life on the street, often related to addiction and mental illness. You might not even notice the chronic homeless in your day to day life.
Apparently, San Francisco does stand out in the high incidence of hardcore homelessness. Supposedly SF and NY have the same number of "hardcore homeless", even though SF has about 1/10 the population (though any time you get into these ratios, you have to remember that SF is a small geographic region and population within much larger bay area - if you drew a 48 square mile border around an urban core in NY or LA, the numbers probably wouldn't look so dramatically different - my guess is that SF would still look bad, but not by anywhere near this order of magnitude).
I would venture to guess it has something to do with blacks having historically been isolated from the opportunities that other races have had, and that even though things have improved, we're still seeing the lasting effects of centuries of prohibitive behavior.
Come to think of it, I've never met a homeless Asian on Indian before. I see plenty of Asians working their asses off in shitty conditions in chinatowns to feed their kids so they can go off to college some day. You're right, it does make you think.
"Yet there are homeless Asians. Isabelle Hsu reports in the Pacific News Service that in San Francisco alone there are approximately 6,000 plus people living in the streets. She quickly adds that this is a very rough estimate. Ed Jew (the only Chinese American on Mayor Gavin Newsom’s committee to end chronic homelessness) explains that the official estimate of Asian homelessness is probably low because of cultural sensitivities. It is also a matter of saving face: homeless Asians refuse to go to shelters and admit to their homelessness."
There is some truth to this:
"According to the Substance Abuse and Mental Health Services Administration, 20 to 25% of the homeless population in the United States suffers from some form of severe mental illness."[1]
Mental disorders prevent people from carrying out essential aspects of daily life, such as self-care, household management and interpersonal relationships. Homeless people with mental disorders remain homeless for longer and have less contact with family and friends. Any type of help from friends and family can be misinterpreted and further pushed towards the cycle of poverty.
you are doing it wrong. very wrong, if you think that's a police problem.
recently the former, most retarded, mayor of Sao Paulo used police on the city's 'tenderloin' (called cracoloandia ...literal translation to crack-land... you get the idea) it resulted in a city wide chaos as those figures, usually restricted geographically and living with their own morals and codes, scattered all over the place and freaked out when found in a situation worse than they were already at, resulted in far worse crimes than the littering they were committing before.
So the absence of homeless is usually not a sign of better humanity, it is usually a sign of cruelty. This is especially the case in the US. There are other countries where they have better treatment for poverty and mental illness (most homeless are mentally ill to some extent) where the absence of homeless on the city streets may mean actual absence of homeless. But this is not the case in the US.
Thus, even if the sight of homeless in San Francisco is so terrible, one should keep in mind that San Francisco provides the best treatment for them in America.