Star Wars: The Last Jedi director Rian Johnson: “I typed Episode VIII out on a MacBook Air. For security it was ‘air-gapped’ — never connected to the internet. I carried it around and used it for nothing except writing the script. I kept it in a safe at Pinewood Studios. I think my producer was constantly horrified I would leave it in a coffee shop.”
I bet a lot of people in his industry do similar things, especially for blockbusters.