Fines are meant to serve as a deterrent. They are set high enough to get broad compliance; even if only a small percentage of offenders are caught. When you make it virtually certain that offenders (or innocent registered car owners) get caught — there's no justification for keeping the fine so high.
Any amount of a fine higher than necessary to achieve compliance with the law; is simply a cash grab.
** (Don't get me started on the horrors of becoming a surveillance society.)
Mostly, fines are a source of revenue. Since CA has gotten into the revenue problems recently, the number of cars pulled over has doubled. Typically, cops stage themselves where it is easiest to get a violation, not where the violations would be the most dangerous.
Back when the limit was 55, AZ cops would stage traps with plans way out in the desert while on the interstate through town, the chief of police was explaining to people why they were not ticketing speeders because those callers did not understand traffic flow! Duh ...