Because to be criminally liable for something requires both a) actually doing something that is against the law and b) doing so with intent (i.e. you knew what you're doing is against the law and you did it anyway... because you thought you will not get caught or just didn't care). It is then up to the prosecution to prove, beyond reasonable doubt, that you actually intended to break the law. (With the exception of strict liability crimes, which are limited in scope to minor infractions and things like drunk driving or statutory rape.)
You can still get sued in civil court of course, but that's not the state trying to put you in a cage and so the standard goes from beyond reasonable doubt to most likely.
If you're a coder coding shady shit for your shady employer, you most likely know you're doing so and there's typically some trace or record left. But coders are not investment bankers and in fact may not even know anything about investment laws and regulations. And it's completely unreasonable to expect them to know. I worked on many projects, including medical and education... if I had to question and investigate every executive decision impacting my work then I wouldn't get anything done.
"Mens rea" is a requirement for certain crimes, but not all, you definitely can be criminally liable for doing something without intent. The trivial example is murder vs manslaughter, the latter does not require intent but obviously can be and is criminally prosecuted.
Furthermore, even in cases where mens rea is required, it gets satisfied if you intended to achieve the prohibited result even if you thought that the result was permitted. "Intent" is not about intent to break the law, it's about the intent to do the thing that happens to be illegal. In this case, it matters if you knew what the thing you're making was going to be used for (e.g. hide some stuff from auditors) but your knowledge or ignorance of the relevant laws and regulations doesn't matter at all - as another poster noted, https://en.wikipedia.org/wiki/Ignorantia_juris_non_excusat .
Sorry but this is completely wrong. “Mens rea” means knowing you were doing a particular thing. It doesn’t mean knowing that it was illegal.
E.g. if I take your wallet off of a table because I thought it was mine, I’m probably not guilty of theft. If I took it because I didn’t know theft was illegal, I probably still am.
You can still get sued in civil court of course, but that's not the state trying to put you in a cage and so the standard goes from beyond reasonable doubt to most likely.
If you're a coder coding shady shit for your shady employer, you most likely know you're doing so and there's typically some trace or record left. But coders are not investment bankers and in fact may not even know anything about investment laws and regulations. And it's completely unreasonable to expect them to know. I worked on many projects, including medical and education... if I had to question and investigate every executive decision impacting my work then I wouldn't get anything done.