The reason why is because sin defines the perpetrator, and definitions are timeless. The forces cause perpetrators of sin to conceal, deny and rationalize the sin. That reaction defines sin, and it leads to more sin. If these concept are difficult to understand or accept, look at crime. It does the same thing, because it is sin which is so obvious that even atheists accept it as wrong.
Crime has to be concealed, denied and rationalized, because everyone feels threatened by it.
Crime demonstrates the objective truth about sin. As an attitude, it is called pride. Functionally, it is the desire to dominate. Morality is most basically defined by intentions rather than actions, because decisions begin with intentions, and there is qualitative content to intentions determining the specific complexities apart from external factors which can alter the results of actions. For this reason, sin and conspiracy are used as approximate synonyms in the Bible.