I know your comment is regards to West Coast cities, but if you've been to the East it's quite noticeable in many cities (Baltimore, Philadelphia, Detroit, among many) - definitely not a uniquely SF phenomena. Did you know that in 2011, there were 46.2 million US residents at or below the poverty line [1]? That's 15% of the US population. And as much as 10% of the poor, or 1% of the US population is homeless [2].

[1] https://www.census.gov/hhes/www/poverty/about/overview/ [2] https://en.wikipedia.org/wiki/Homelessness_in_the_United_Sta...