One can say law shouldn't pursue people for small infractions (speeding, running stop signs, etc), but if they don't we'd see an awful lot more of people running from the law.
As it stands right now, people generally run because of something much larger than the observed infraction. They are either drunk, carrying drugs, have no license/insurance, etc.
While this sucks all the way around, it can be laid squarely at the feet of the pickup driver. His family sure wouldn't want me on the jury if they sued for wrongful death.