e.g. from https://www.theguardian.com/business/2012/dec/14/hsbc-money-...
"In some branches the boxes of cash being deposited were so big the tellers' windows had to be enlarged."
This entire subthread is about how AML is enforced. Specifically, it's enforced by regulators doing whatever they feel they need to do. The punishment wasn't for money laundering, it's for money laundering in a manner that obedience, according to the regulators, would have caught.
For international banks, it's especially arbitrary because regulations are so loose overseas. In the UK it's very easy to move small amounts anonymously. This is routinely used for small-time laundering by organized crime and banks are fully aware of it. The long arm of US law goes after UK banks handling Mexican dirty money, but not UK banks handling UK dirty money. A lot of what constitutes "illegal money laundering" is actually political.
And the bank has to do it or they end up like HSBC. In fact, that was exactly why HSBC was fined billions. Regulators told them to do specific things, like use Form X in Iran instead of Form Y, or classify Mexico with risk measure N+1 instead of N, and they didn't do them. This is all in the various public records.