Ok, here it is then: I agree with this logic that the reason for making an explicit rejection of innocence as an excuse has to do with the possibility/likelihood of people using ignorance as an excuse for transgressions that lack immediate consequences strong enough to deter them from violating the law.

However, I still contend that this attitude exists both within violations of statutory law as well as more natural/physical laws. E.g. While the law of gravity may result in immediate consequences when you walk off a cliff (provided you're not a cartoon character), its consequences are less immediate when it comes to something like building on soft ground. So it IS possible for people to ignore the physical consequence of something like building on soft ground even though they should understand that their ignorance won't protect their building from falling down.

So when people don't believe in longer-term consequences for their actions, such as climate change or running out of money, the essential meaning of Ignorantia juris non excusat applies in the same way, i.e. that people will claim ignorance and thus complain that it is unfair for them to suffer the consequences of their actions, even though they should have understood the inevitability of those consequences by understanding the overall mechanics of the physical universe.