And then you would have to prove your insanity. If you cannot prove it, then either you will be given the ticket anyways or you may very well be charged with lying to an officer or some such thing, and also wasting their time. If you can prove insanity then you will be legally insane, that means you cannot drive anymore, you lose a lot of other things, and the state can lock you away in an asylem if they feel you may be a hazard to the public (and if you are getting a speeding ticket, and are proven to be insane, then I think they have more than enough to lock you away).
It's easier to just be responsible and suck up to the fact that you were speeding and you need to face the consequences of your actions.