Municipalities use traffic fines for funding. Like property taxes, sales taxes etc. I'm sure you've heard of Police Quotas for traffic tickets...

You really should read the link I provided above. Especially the story about San Diego, CA and their abuse of traffic cameras and how they did an under-the-table deal with the company who installs the cameras and offered them a "commission" on all the traffic fines generated by their cameras.

I'm not coming to the defense of the poster, I drive overly safe on the streets and wish everyone else would as well... But, cities have always abused the issuance of traffic citations to generate income.