The VA can't force people to accept help, especially those who are substance abusers.
I know from experience that our local VA seeks out the homeless veterans, and offers them services beyond even those required by statute. I also know that if any civilian staff at the hospitals or clinics doesn't show proper respect or service to a veteran, they are dealt with firmly and quickly. I can't go into details but I was involved in just such a situation. The administration, without any prompting or complaint from me, took the initiative to resolve a problem with one of the staffers; it shocked me how quickly and seriously it was dealt with. Also, the VA departments are constantly sending out surveys and requesting feedback from veterans about their services. It's almost annoying (in a good way). They do community "Stand Downs" for homeless veterans, like an open house, to draw them in. They set up their service areas where it is most convenient for the downtown homeless vets to access.
The truth is, some vets spend their pensions on booze and drugs, and cut themselves off from family members who are searching for them. Also, it's been discovered that quite a few homeless guys who claim to be war veterans, are not. Anyone can buy surplus uniforms and hold up a sign that says "homeless veteran." But after a little questioning, it's clear that the person never served in the military.
I'm not saying that there isn't a problem. I'm saying that it's not all about the country ignoring it's veterans. But we can always do more for them, that's for sure.