The rationale behind an SOL is to afford protection to a defendant against stale claims after a significant period of time has elapsed, during which a diligent person would have accused the defendant.
With the passage of time, memories fade and witnesses may move, vanish or die. Scientific studies confirm that the passage of time erodes or even rewrites witness memory.
At the same time, statutes of limitations exact a toll on justice. They are, by definition, completely arbitrary. They make no distinction between just and unjust claims. They are also completely inconsistent from state to state and federal law.