Answers:
Convictions lead to points on your license. This can increase the cost of car insurance, and if you get too many points you may be classified as a negligent operator and can have your license taken away. Commercial drivers (trucks, big rigs) can't even have one point on their licenses, which means that one simple ticket can lead to job loss. And while ordinary drivers can go to traffic school to have points removed, commercial drivers are not eligible. Anyone who's a professional driver needs to fight every ticket (infractions as well as misdemeanors). Even a minor $300 ticket means your livelihood is at risk.