Just to say though, the groin isn't always an easy target to get at ( I know I know "Speak for youself" lol!).
Additionally, it's not as far fetched to think people may not feel pain in the groin. If a person is high or very drunk possibly it may temporarily negate the sensation of pain.
Also, as rare as it would be to meet someone who does it, Shaolin monks have exercises to condition and protect their groin:
Matthew Polly in his great book "American Shaolin" attests to witnessing first hand to a monk being kicked hard downstairs while wearing no protective gear. Polly states that as fact as he was asked to come out of the audience and kick the monk himself!!!
"Let your food be your medicine, and your medicine be your food"