American shakedown: Police won't charge you, but they'll grab your money

  SULPHUR [Louisiana], POPULATION 20,552, ILLUSTRATES THE transforming power of civil 
  forfeiture. It is a modest Southern town with one main drag, but at its north 
  end stands a modernistic new office building. Outside its tinted windows and 
  trim lawn, the well-swept Tarmac is crowded with rows of gleaming 
  blue-and-white cruisers and sporty unmarked coupes, many of them equipped 
  with video cameras and computers. The building, cars and gear all belong to 
  the Sulphur Police Department.
  
  The day after my run-in with the drug-interdiction cops, I talk with Keith 
  Andrus, supervisor of investigations for Sulphur's narcotics division. How 
  does Sulphur manage to pay for the Police Department's new building, the cars 
  and computers?
  
  Andrus smiles and points to a framed news item on the wall: "Traffic 
  Violation Yields Police $532,100." An inset photo shows Andrus with a fellow 
  officer beaming from behind a table heaped with stacks of cash. Typically, a 
  speeder is pulled aside. When a lot of cash is found on him and his 
  explanation is suspect, a drug dog is summoned. If the dog smells narcotics, 
  the police seize the money. Because dollar bills are routinely used for 
  packaging and sniffing cocaine, and the minutest trace of the drug will 
  "infect" other bills, much of the currency in the country now tests positive 
  for narcotics.

Is it typical in the US to carry cash in the tens of thousands of dollars? While I understand some people are unbanked, surely it is possible to open a bank account if you have tens of thousands to deposit. Leaving aside whether it is legal to seize the money or whether it is ethical to do so, is there a good reason why you would choose to walk around with, say, $100,000 in cash instead of a bank cheque or a a plastic card?

They're fishing for literally anything. They don't care whether it's cash, drugs, paperwork violations. It's all money in state coffers at the end of the day. It just makes the news when they seize some sympathetic person's cash. You don't hear about all the innocent people who get railroaded on DUI charges and come out $10k poorer because of it (I specifically use this example because many states and municipalities have had scandals to this tune). The fact that the cash seizures are blatantly unconstitutional just makes them marketable to the public but the root problem is that the police (as organizations more than individuals) see the public as people who's pockets ought to be lightened and they have no moral qualms about engaging in "scummy but legal" means to do so.