The real reason is Finnish absolutely draconian fines that scale up with income and really really strict enforcement. Make fines start with $500 and go to thousands and actually enforce them and not what SF is doing and we'll have the same but people over here don't like to hear it...
do they charge as a % of annual income or wealth? I think that would be the key in the USA. I'll risk a $300 ticket for speeding, probably not a $3000 ticket