Your problem is not unusual. I have seen and heard this for years. Some parents have financial issues they don't want to share with anyone, anything. They also may not have filed taxes. They also may just be too disorganized and depressed to get it together. Some feel the kid isn't getting anything much anyways, and though I don't support the reasoning, they are usually right.
If your family is making a true middle class income, you aren't going to get anything more from the government that the loans. $5500 freshman year. In some states like NY, there are state funds, but the list is short. If they refuse to have anything to do with the FAFSA, yes, you can get the loans on an unsubsidized basis. Find out what they are willing to pay for college, and if it's three squares and cot, you commute. That's about $10K a year over going away to school. THen you find a job, get the unsub loan, and scrape what you can out of them. That's actually a typically scenario.
As to why it is difficult to be deemed independent, it's because enough people try that route for too scarce resources as it is and there isn't the money. It's all one big business and without parents willing to pay for the kids, a lot would go bust since kids 18-24 don't tend to have money; they tend to be broke and dependent on their parents financially. Why do robbers go for banks? It's where the money is!