Insurance company rate schedules must be approved by the state’s insurance commissioner (IC). The IC is selected by the governor of the state or sometimes elected by the people of the state. The IC acts in the best interests of the consumers of the state, not in the best interests of the insurance companies. So, yes, technically a company can charge what it wants to whom it wants, but not if the IC rejects those conditions.
In order to get a rate schedule approved, the insurance company must show actuarial data illustrating why some drivers will be charged differently from others. The most common criteria include the age, gender, years of driving experience and 3-5 year motor vehicle record. A few years ago, credit history was discovered to be a stronger indicator of potential for losses than even your actual driving record. My own experience has shown me that people in certain occupations are more risky (clergy & insurance agents, oddly enough are abysmal) while other drivers are less prone to have an accident.
The reality is, every insurance company is different and pays attention to different things. If there is a group of people who get a break that you don’t, the correct assumption is likely to be: there is data to support the discrimination.