The reason why is that most cars do not have a interceptor or severe duty version. The Crown Vic is one of the few that have Taxi and Cop packages. In the states there are very few places that you need to be really fast or handle amazing.

Most states have to call off high speed pursuits if they are close to cities, and the highway patrol is faster than the fastest dragster, and handle better than a sport bike or Porsche. They use Radios to move great distances without burning a drop of fuel and they can be in 2 places at once. The vehicle is not used very often to catch anyone, the radios is a better choice.