As a simplified and extreme example just for illustration, imagine a launderer going to a million gas stations and buying a $1 lottery ticket in cash from each

As a simplified and extreme example just for illustration, imagine a launderer going to a million gas stations and buying a $1 lottery ticket in cash from each one until they've got most the tickets. When they win the lottery, one gas station reports the winnings of $800,000 on a $1 bet. Launderer reports earning $1 selling a Pokémon card, and $800,000 winning the lottery. Other gas stations and dirty income, unreported, as small losses dont require individual reporting. End result is $800,000 clean on $1,000,000 of dirty money and only $1 has to be explained. For casinos, it's likely something closer to buying chips under the reporting threshold, losing most of them, and keeping on until winning a longshot bet. Or just claiming they are a card counter or some nonsense as to how they keep it up. The fact they lose some money to the house is just the cost of doing business. The fact winnings are reported, desirable.