Charity exists on a scale from very considered to not at all considered, same scale with not very effective/$ to very effective/$. There are meta-charities that

Charity exists on a scale from very considered to not at all considered, same scale with not very effective/$ to very effective/$. There are meta-charities that try to evaluate the effectiveness of other charities. The point is that this is at the "not considered/effective" end of the scale. The really pressing problems of the world aren't American homelessness, and homelessness is not a cost effective problem to try and solve (compared to eg. people dying of water-borne diseases in the third world). So he either hasn't thought about it, or doesn't really care (and the two are connected one implies the other).