You bring up a great point about selection bias. The "homeless" you see are the ones with the drug/mental illness problems. When I was in college 2 of my friends were homeless. One slept in his car, the other slept in an office building. I would have never known if they hadn't told me.
Ya, we really shouldn’t forget about them. As an 18 year old, I slept in my car for a few days before so I can totally empathize.
It is really sad that we have equated drug addiction with homelessness. We should really treat them as separate problems, since one is much easier to solve with social resources than the other.
