Hmmmmmm I'm not sure about non-wheel-shaped steering wheels. In an emergency situation (i.e. losing control of the vehicle) it seems likely that muscle memory is going to kick in for regaining control and having an odd-shaped wheel could be an issue there. I've not checked of there's any research on that but it would be my gut feeling
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I also don't think there's any good reason for it other than "to be different".