What makes people ignore the homeless is the fact that there are hundreds if not thousands of them roaming the streets of major (and not so major) cities. When I was in Regina, you couldn't walk 4 blocks without being accosted with demands for money, cigarettes, etc.
After a year or so of living there I used to just give them the finger and keep walking. It's not that I'm heartless -- I just don't care to be badgered everywhere I go when these lazy fucks could go on welfare and be housed like anyone else. Aside from that, I'm on disability -- I have no more money to spare than someone on welfare after I pay for my meds. Adding to that, I'd actually stopped to talk to and gotten to know a few of them, and found most of them were *on* welfare and did their begging to pay for booze and drugs, not because they needed the money to survive.
Sympathy. You'll find it between "shit" and "syphilis".