Standard auto insurance means that auto insurance company considered the drivers to fall into an average risk profile. The company charged the premium based on actuarial information compiled from similar drivers in the past. Insurance company need to be able to estimate the risk in underwriting new policy, or else it can break or make the company. It can be profitable or they can wind up paying out more benefits that receiving premiums if they do not understand the risk effectively. 

Insurance companies, in this case auto insurance, will consider driver's age, driving record, car usage, credit history, and location. They also will compare the driver's characteristics with actuarial information. The actuarial information helps the insurance company to determine the time frame of the driver "will getting into an accident". The company use this information to set the premium that charged to the insurer as well. That's why insurance company have to fully understand and pay close attention to individuals and business when underwriting a new policy.

There are three categories the insurers use to divide the drivers: preferred, standard, and substandard. Preferred is usually the least risky drivers based on their driving history and vehicle usage characteristic, so that the drivers offered the lower premium. Standard drivers are average in term of risk and get regular premium. The most risky is substandard; they are either pay highest premium or denied in getting coverage.

Standard drivers do not mean they have perfect driving record. They are most likely have long driving experience, good credit history, do not own sports car and use their vehicle for commuting short distance (relatively).