Because you let him drive your car. Please contact a traffic citation clinic see if there is a way around, or if you can ask the court for relief.
First of all, sorry about your situation.
I disagree with the previous answer. There is no local clinic to help. Also, it doesn't appear that you gave him permission.
You need to go there and make a stink that your friend didn't have permission and provide proof of ownership and insurance. You go to the arresting agency.
Be careful because he may end up getting charged with theft, but if really didn't have permission, then that is what is was.
Good luck with the situation. The above is general information and not specific advice.
Matthew Williamson, Attorney
Monterey, Salinas, and Santa Cruz