A lot of people keep good luck charms in their cars, even if they're not really thought of in that way. Such an adornment could be as obvious as a picture of a Catholic saint taped to the dashboard, or as subtle as a photo of the family tucked away in the glove compartment. Of course, lucky coins or rabbit-foot key chains are other examples of this custom. And it makes sense. We spend a lot of time in our cars, and they can be dangerous, so a token of significance can help put the mind at ease.
We can't really blame pro racers for doing the same thing. Tazio Nuvolari, and Italian motorcycle racer and racecar driver, wore a tortoise pin as his lucky charm. The pin itself might have been unique, but the idea of hiding a talisman under clothing is not. Sebastian Vettel, a German Formula One driver, is rumored to keep a lucky coin tucked somewhere nearby. Other racers, over the years, have admitted to doing the same thing, and it's fairly easy to imagine there are many more that have chosen to keep that information to themselves. It's an easy (and personal) way to bring a little bit of comfort to a driver during all those lonely laps.