Not everyone has a family to fall back on, people lose there job, can't pay the rent and get the

treatment from the landlord and well...
Also mental illness is another reason.
Its crazy that Homeless people even bother to continue living, if you're out on the street there isn't much to look forward to life.. its crazy established people commit that over someone breaking up with them but homeless people who have no hope of getting in a relationship or someone to voluntary have sex with them keep on pushing