Illegal immigrants are completely off the grid, which makes them hard to track and crack down on. By allowing undocumented immigrants driver's licenses, the government has a way to keep an eye on illegal laborers, and on employers who exploit them to get around tax laws and minimum wage laws. Additionally, many of these workers are going to be driving anyway, and it's a good idea to make sure they actually can.
A driver's license provides a person with more flexibility and mobility. A mobile person spends more money at local businesses and also has greater opportunities for work. By granting licenses to illegal immigrants, America is giving them the chance to contribute to the society around them. Licenses benefit the immigrants further by pointing them in the direction of citizenship.
Obtaining a driver's license is not akin to citizenship and it should be made clear to illegal immigrants that seeking a driver's license may lead to their detainment or deportation. They should, however, be given the option to seek them. If they are going to be here in the United States for any period of time, then they should be productive members of society. Getting to and from a job often requires an automobile. Plus, if they should attempt to drive without a license and get into an accident, then the other motorist suffers because they were not able to obtain proper driver's credential and, subsequently, insurance coverage.
A driver's license is a privilege, not a right. An illegal immigrant has not earned that privilege because he or she has not taken the necessary steps to become a legal citizen of this country. Plus, these immigrants must understand the driving laws of this country just as legal citizens do.