I'll do my best to give some reasons but this list is by no means exhaustive. In general I would say there are two main issues at play, one is that SF is relati

I'll do my best to give some reasons but this list is by no means exhaustive. In general I would say there are two main issues at play, one is that SF is relatively welcoming of homeless people, the second is that most other US cities are incredibly unwelcoming. So you end up with a homeless population both being pulled to SF and at the same time pushed into SF by other cities. Some of this is simple geography. It's much easier to be homeless in a dense (by US standards) city than a sprawled out suburb. SF also has decent public transit, again largely due to the necessary density, which makes being homeless easier. SF also has a relatively mild climate. Yes, the fog and the dampness/rain do suck, but it rarely gets either extremely cold or hot. Outside of geography, some cities are known for being extremely hostile to the homeless through policy and actively try and push their homeless out. I believe some cities, Las Vegas if my memory is correct, have been caught giving bus tickets to SF to their homeless. I know there are cities in Orange County where the police have been known to pick up homeless people and drop them off in neighboring cities. So, SF tends to get stuck with homeless problems that should be shared between many other cities/regions. SF also tends to have pretty good homeless services in terms of things like food kitchens and temporary housing/shelters. I will also add that having grown up partly in SF, and having spent some time living on the streets (more accurately parks) there, I don't think SF's reputation as a dirty city is entirely due to the homeless population. The people in SF, even those with multi million dollars houses, just don't really seem to care much. I've seen plenty of what I assume to be well employed people litter and no one really bats an eye. It also isn't unusual to see non-homeless people urinating in the streets after bars close. Again, I just don't think there is a critical mass of people that care enough, and I get the strong impression that those that do care don't really want to say anything since it could be interpreted as being intolerant. I think the fact that you have a large number of young single tech workers who probably don't have plans to stay in the city long term leads to a lack of civic pride. Additionally, while there are many wonderful aspects of the tolerance that SF is know for, I do believe that many people end up being too accepting of what is and isn't acceptable public behavior. This is probably complicated by the fact that I don't actually think SF is nearly as progressive as it claims, it's mostly virtue signaling. It's much easier to say you're progressive by tolerating all sort of behaviors that aren't particularly healthy, than it is to try and help the underlying causes of those behaviors. It's very late here so my apologies if this wasn't a good explanation.