I might be wrong, but I always lean towards this being the result of prioritization. Most engineers know the difference but prioritize other aspects than ethical. I am not even judging that, just describing. After all, implementing a dark UX pattern that will inconvenience some unknown to you users is not as high priority as providing to your own family.

It's a different mindset. When you're in uniform, under oath, you don't speak out, you salute and do what you're ordered to. When you retire, you take the uniform off and are your own man again.