The reason why I wouldn't give consent even though there is literally 0% chance of finding anything wrong, is that from what I understand: If I tell a cop go ahead and search and he yanks my laptop bag out of the car and throws it to the ground, then I am on the hook for replacing my laptop. On the other hand, if I say no to a search and he does it anyways, I have grounds to sue since he destroyed my laptop by dropping it on the ground in an illegal search. If I am doing nothing wrong and am not a suspect in anything, then I see no reason why I should be the one "on the hook" for saying go ahead as a way to "prove" my innocence. He can call drug sniffing dogs or whatever, but it still won't change my position.