When it comes to homelessness, almost every story pivots to California. The Golden State has about a third of the nation’s homeless population, making it a test kitchen for ideas, a subject of pity and scorn and a cautionary tale as homelessness grows around the country. So why is homelessness so much worse in Los Angeles than in other parts of the country, even as other cities also combat poverty, drug addiction and crime — and enjoy warm weather like L.A.’s?