partly this. ive seen this too, albeit its rare where i am. the other side of the coin is that whether by your fault or someone else's, society forgets who you are. in turn, theres now a lot of "inertia" to your homelessness. you might literally have to put up with bumming donations to save up the meager amount youd need to get food/booze/drugs/help/shelter; especially so if youre unwilling to be a criminal.
United States