You just described the problem exactly. Instead of getting elected based on principled issues such as "America's prison population is out of control. We should reform the justice system to easier for citizens to understand", the only way to get elected is target some special interest group. You stand a better chance of getting elected on some relatively unknown issue that is relevant in a handful of people's lives than something based on principles.
The majority of Americans do not care at all about politics. Ignorance is a rational choice in the face of the enormity of the American Federal government alone. They don't care that if you started reading the Federal Register for last year today, you would die before you finished. They don't care that if you tried to be a good citizen and understand just the tax codes that apply to you, you'd never figure it out because it changes faster than you can learn it.
The majority of Americans do not care at all about politics. Ignorance is a rational choice in the face of the enormity of the American Federal government alone. They don't care that if you started reading the Federal Register for last year today, you would die before you finished. They don't care that if you tried to be a good citizen and understand just the tax codes that apply to you, you'd never figure it out because it changes faster than you can learn it.