They are US citizens and they can leave anytime. Furthermore, poverty is not a barrier to picking up and leaving.
I'm guessing you're not part of a minority.
They could, technically, 'leave anytime,' sure. And be homeless somewhere. Most of them are unemployable; after all, they have a big black mark on their resumes: they've been living all their lives, unemployed, on the most high-crime res in the region. Would you hire someone with that resume?
It's very hard to get out of a ghetto situation. Not only are they undereducated, but they have no opportunity to find work. It's hard to get a new home elsewhere when you've only ever known the res, and don't have the opportunity for work elsewhere. It's a rotten situation up one side, and down the other.
These communities are already getting massive amounts of help.
First off, you're wrong. They receive very little (a couple hundred/month if they enroll in a special welfare program. That's it.) In the 90s, the government built a bunch of houses, and moved everyone into odd little communities. Those have seen fallen into states of disrepair, as nobody could afford to live in them; lipstick on a pig and all that. They need education above all else.
But more to the point, I never said they needed Federal aid. As a libertarian, I believe strongly in private aid organizations (my favorite charity is a particular homeless shelter which is completely privately funded.)
Have you ever been on the Pine Ridge Res? If not, you have no idea what life there is like. I have traveled the western half of the USA, and have never seen a res as depressing and dismal as this. Even the Rosebud reservation, just a couple hours to the East, is substantially better. But if you recall in your history books, the Sioux, specifically the Oglala Lakota, were despised for their refusal to surrender to the USA. They're the tribe that ambushed Gen. Custer. They've never been seen as equals with the rest of America, and the bad situation 100 years ago has lead to the bad situation they live in today.
A computer without COBOL and Fortran is like a piece of chocolate cake without ketchup and mustard.