Instead of basing your thoughts on personal anecdotes you should look towards statistics. For instance the New York City Department of Homeless Services estimated, in 2013, they had almost 50,000 homeless living in the city[1]. But this is just an example; you can look at a huge variety of statistics for many types of places to see how widespread the issues are.
Overall there are over 500,000 homeless people in America on any given night[2]. There are real problems.
[1] https://en.wikipedia.org/wiki/Homelessness_in_the_United_Sta... (shitty source I know; it references a dead article but this is mostly just an example).
[2] http://www.endhomelessness.org/library/entry/the-state-of-ho... (though perhaps a little bit of a bias source; sorry didn't feel like reading too deeply into the government documents to find their data)
I've only ever had that experience while visiting SF.
You said yourself you've been lucky enough to live and work in particularly nice parts of town. That sort of makes your dispute moot, and I still ask, "so does that mean the issue doesn't exist?"
