why should someone have a rap sheet or record?
commit crime, get caught, do time/pay fine(whatever punishment)...then you are square with the house, back to zero.
Because criminal histories are an excellent predictor of future criminal behavior. You can look at a criminal's history and read it like a crystal ball as to what they will most likely do in the future.
Federal Sentencing Guidelines are built on this concept. They increase exponentially with an offender's criminal history. It is broken down into six categories. I being none VI being a career criminal. The penalties are radically different for an offender based on their prior record. The guidelines do cut you a break that if you have gone 10 consecutive years with no crimes then it starts back at level I .
Most states use a similar model.