There are so many reasons it's difficult to begin.

The drug addicts and scammers, and there are a lot, are fully functional and remorseless and natural scammers. They see everything in life as a scam and they should scam as well. They can work the system, lie the best, scream the loudest.

There are many homeless who are not really mentally ill or addicts. If you don't like handouts and are quiet and respectful, your chances of getting help are drastically reduced. The vast majority of aid workers, professional and volunteers, are good people who are stretched to their limits. There is only so much attention to go around, even if resources are more or less abundant.

The daunting amount of red tape and paperwork is a job in and of itself. The amount of work you have to do to get benefits not just from the Feds but deserved VA benefits is incredible. It's a job. Meanwhile your phone number has changed, address has changed, things have been stolen... Think of getting your wallet stolen, all your papers ruined or stolen, moving, losing a car, job, all your social contacts, all at the same time. Then do that once a month. That's what being homeless can be like.

There are also an incredible number of 'free spirits' who don't look like hippies who are just street people. Other people are not really mentally 'ill' as much as they are broken and unwilling to trust anyone for anything at all, ever. They've just been taken advantage of so viciously so often for so long that they have decided this is where they are staying, at least this is a known.

The situation is changing, though. The scumbags are still working the system and taking the same amount but some help is getting down to people who are sincerely in trouble or just lost and hopeless. Which I think is logical. If there was some way to get rid of the parasites it would be nice but since they aren't going anywhere and take advantage anyway, governments are at least getting help to people who really need it at this point. Besides the incorrigible druggies, there are sincerely drug addicted and alcoholically-ill people who are the most difficult to care for. I'd say that >50% of the drug addicted homeless are there by choice and could quit if they wanted to. For alkies, it runs about >75% in my experience. Alcoholism is very difficult and there is little available that seems to help a true alcoholic, not some David Letterman douchebag but someone who takes a drink then is gone for 3 months. Nearly unsolvable problem, that.