There’s nothing morally wrong with moving money around for people without validating their identity.
But if you make it illegal than almost everyone doing it will be doing it to launder money or evade taxes, so if you catch someone at that, it’s almost certain that they have either committed another crime or have assisted someone else at committing a crime.
The alternative to having financial crimes like that is that it becomes impossible to convict the upper levels of crime organizations of anything, and you just end up arresting low level people for crimes where you have immediate physical evidence.
https://amp.cnn.com/money/2013/02/28/news/economy/illegal-in...
https://www.latimes.com/business/la-fi-bitcoin-sentencing-20...
IANAL but surely laundering known drug money with gold/diamonds/beanie babies/bitcoin are all illegal.
Pedantically, yes--there would be one fewer crimes committed. Practically, not reporting income hints at knowing its source isn't entirely legal.
Some like the individual in the article will end up being examples to others.
But maybe that is typical when doing illegal transactions.
With the rise of strict liability crimes for everything this balance is no longer in place. The Overton window has moved dramatically from where it was when that phrase was coined.