Because he used to be a REAL Marine DI before acting.
I’d imagine he was far scarier in real life...
I saw him at the NRA Convention in Charlotte a few years ago. He’s a short, wiry old guy.
I recall a documentary on Marine boot camp not long ago. They talked about how the DI’s was no longer allowed to strike the recruits. Gunny was interviewed and he said that if he is able to “put my hands on you” you will remember what I’m teaching you. Pain is a good teacher.
A couple years after boot camp we were preparing for an IG inspection. Me and two others went fishing and were studying while fishing (and drinking). When one of us would get an answer wrong another would hit them with a stick. It didn’t take long to learn what we needed to know.