Most crimes of all sorts go unresolved. Even most outright murders... are unresolved (no conviction) at about the rate as hit and runs (involving a cyclist or not). I think people that expect arrests and convictions.... have maybe watched a little too much CSI (or other TV programs). I don't really understand what some people expect from the justice system. Or for that matter... what they think justice is.
I for one... if I am ran-over and killed while cycling. Won't rest better is some young drunken "lady" is imprisoned for a decade. While her children drift from home to home thru the child welfare system. It isn't that I don't want justice. It is I can't imagine what "justice" would look like. I do understand revenge... and I know what it looks like. But I don't carry that much fear or hatred around with me. I wouldn't want to live that way.