the selfish and non-obvious reason(s) to do no "evil"
while there are probably a plethora of reasons to "do no evil" for external reasons like not being punished or not being wracked by your conscience or not having karma rebound on you, it has dawned on me there are even more compelling reasons.
this particular reasoning would only apply if you're not a psychopath (though even psychopaths would be punished by other cognitive penalties in the material/external world for their misdeeds), but having a clear conscience removes things that your mind can use as ammunition. a clear conscience gives your mind one less thing to chew on. and the less your mind has to chew on, the less crap your attention is forced to attend to. the less content or crap your attention attends to, the more mental RAM is freed up. more mental RAM gives you more working memory to process more cognitively demanding things AND be able to perceive things that would be impossible for you to perceive otherwise. it can be considered superhuman level of awareness or perception though it is theoretically available to anyone. for e.g. it took boundless awareness to cure my bipolar disorder which has no known cure. and instantly, permanently, and effortlessly break my heroin or smoking addiction. that level of awareness is literally godlike in power and is actually what the mystics actually referred to when talking about the divine or god. there are like an infinite array of unknown things one does not even know of and you will need every ounce of mental RAM and present attention to be aware of opportunities that would benefit you or things you can learn that would be impactful or transformational.
the world is already virtually infinitely complex, layered, and diverse. doing no "evil" to have a clear conscience is one part, but of course not sufficient either. for e.g. if you are autistic or have low self esteem, not doing "evil" isn't sufficient. if you do "evil" as someone with low self esteem, you may end up psychotic and in a really bad spot. but not doing it isn't enough to have a sufficiently free attention because attention will still be forced and stuck on self preservation. but at least, having a clear conscience makes it easier to then unravel/dismantle the sources of that low self esteem. having low self esteem and believing you aren't even worth saving is a disastrous combination because your conscience won't even allow you to save or help yourself. there is perhaps a way out of that situation as i've been there, but that is not a situation you probably want to be in the first place.
if attention is not stuck and looping due to conscience or lower self preservation, attention can be freed to explore and be open to ripe opportunities which will only be of benefit to the person. and positive sum success will be of benefit to not only that person, but people or beings other than that person.
i love having a clear conscience. it is way more durable than doing something wrong for some material thing whose pleasure is momentarily. the guilt of doing something wrong not only has the emotional and psychological penalty of guilt or shame or inhibition, but adds a psychological and cognitive load that can last really long and have a negative experience with a greater peak. awareness and attention will not be able to flow or expand as much. a clear conscience has helped in the realizations of major revelations, transformations, and opportunities. for e.g. finally be able to grok social dynamics in an office environment after 32 years as someone with autism or being aware of relational opportunities with people who may be of my tribe or being open to the level of awareness that can instantly and "permanently" break a smoking addiction.