Criminals performing illicit activities prefer to use cash as their primary financial instrument to facilitate their transactions. Given its anonymity and privacy, authorities around the world face difficulty in tracking criminals down. However, cash has its drawbacks. The smaller the denomination of the cash collect can amount to a more substantial weight, which in turn, requires more logistical planning.
This is why many countries around the world are slowly discontinuing their largest notes. The primary reason is to further inconvenience criminals that deal with cash. In 2014, Singapore discontinued its $10,000 bill, giving the Central Bank of Singapore a boost in its anti-money laundering / countering the financing of terrorism regime.