I once saw a bit of film on TV which included video of a dog running, in slow motion, and its testicles were bouncing up and down to a severe degree.
I guess we male runners are little different.
I always wear fairly tight underpants or their equivalent under my shorts to give myself appropriate support down there, to cancel out any downward forces of my running. It's only common sense.
For the same reason, I dislike boxer shorts generally. Where's the support in a pair of boxer shorts when you need it?
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