The other driver may have the called the police on the advice of their insurance carrier or because they were driving a company car and required a police report to document the incident. The reasons for why they called are not as important. From the State’s perspective every accident must be reported. It is the State’s burden to prove beyond a reasonable doubt that you were the person who drove the car. The penalties are severe, but if the other driver does not appear in court the state may not be able to prove its case. If the other driver does appear there is usually an opportunity to work out an agreement that favors all parties.
There is a difference between leaving a scene of an accident causing personal injuries vs. property damage. The court takes much more seriously if you leave the scene of an accident where someone was injured.