Every year, federal and state law enforcement agents seize millions of dollars from civilians during traffic stops, simply by asserting that they believe the money is connected to some illegal activity and without ever pursuing criminal charges. Under federal law and the laws of most states, they are entitled to keep most (and sometimes all) of the money and property they seize. (according to the ACLU).
If you have ever been asked by a cop, "do you have any large amounts of US currency in your vehicle?" it is because the police wanted to steal it.
for a better understanding on why this is important, please watch: