its all a matter of degree, though, isn't it. I must have batted in 1000 cricket games without a helmet without ever getting seriously hit on the head, and the number of people I've seen hit on the head is minimal, and none of them have ever been serious. So I would suggest that the additional risk of batting without a helmet is not zero, but it is very, very small.
That isn't true of the risk of theft of a car if you left your keys in the ignition.
I have lost a tooth because my toddler clumsily whacked the glass I was drinking water out of. Perhaps we should make it compulsory to wear helmets when drinking water in front of toddlers?
Prevention is better than a cure, just because you haven't been seriously hit in 1000 games doesn't mean that it doesn't happen.
I saw two people go to hospital in the same game last season, one with a fractured eye socket that would have 100% been avoided with the use of a helmet.
Sure, you can get hurt whilst wearing a helmet, and you can be fine after getting hit without one, but you can't seriously suggest that the risk of getting hit and seriously injured without a helmet is only marginally higher than being hit with one.
I'm sorry about your tooth, but in that instance, you've been involved in a genuine accident, the most important aspect of which is it's unexpected nature. If you walk out to bat without a helmet, you walk out knowing that there is a chance that you will have a ball directed at your face.