Money laundering is the process of changing large amounts of money obtained from crimes, such as drug trafficking, into origination from a legitimate source.
So with that in mind traditional currency poses problems of its own for investigators. Bank notes are untraceable unless authorities note the serial numbers in advance.
Global banks amassed some $15 billion in fines in 2020 for tacitly enabling money laundering and other financial crimes. No mention of the profits made by banks for laundering, that I could find so I don’t know the margin.
Surprisingly Bitcoin’s transparency may do more to mitigate fraud and theft than traditional banking and currency ever could. Through blockchain recording of all transactions brings its history along with the currency.