It signifies that both parties read, understand, and agree. This is so there are no bent feelings later when two perfectly honorable people disagree on what was agreed upon.
That's fair. I would go work for a competitor and not feel less honorable because I know that company would hire someone from the very same company I now work at and not feel they have done anything wrong.
When you are fighting a power inbalance guile is a very effective tool and nobel trait.
It signifies that both parties read, understand, and agree. This is so there are no bent feelings later when two perfectly honorable people disagree on what was agreed upon.