Drugs are a part of the problem, no doubt.
But there are also those who just dont want to get out of their position. Or their situation is a making of their own. Rather then do something about it, they choose not to.
I also think the government (CA) is partly to blame, by passively encouraging it. Their rules and regulation to build any kind of housing is a detriment to the situation.
It is a problem beyond a simple fix. So those who it impacts, business, local neighborhoods, feel they have to do something.
The fact the government did not remove the rocks, and put them back after someone pushed them into the street tells me they do not want to be responsible in any capacity. Too afraid of upsetting the progressives, and too afraid of upsetting the local tax payers.