Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

How on earth does wearing a helmet stop me -

signing an online petition to prevent helmet compulsion, or
signing an online petition to get a stupidly lenient sentence handed down to a bad driver increased, or
explaining to people how inconclusive helmet safety evidence is so that praising me for wearing one and admonishing someone else for not is fucking stupid, or
etc etc etc

It doesn't, in the same way that the drunk person could look elsewhere for their keys too, possibly even in the correct place.