As like everything... it has to do with money.

The IRS and the federal government take transaction slips for every cash transaction over $10K in america, whether you are buying a car, making a cash bank deposit, ect. They are called either Race 10K or 10K stipulation forms.

Most poker players... especially people who play poker for a living... don't want the IRS or the feds to find out that someone who hasn't pay taxes for 10 year came up with $25K to enter one poker tournament.