It's not that unusual to find wealthy parents that refuse to help their children at all, even though they didn't do anything, and are fine people. I'm a bit unsympathetic to OP, but the young adults that have literally nothing thanks to the whim of some asshole... that's really tough, and a flaw in the system.

Anyway, there are rare cases, I believe, but the government makes this very difficult. If you grew up in a normal household, live an ordinary life, but your parents refuse to pay, you're out of luck. You will struggle to get this even if you're estranged from extremely abusive parents.