Everywhere I've ever worked, if I went to management and said "hey, I've got some files from my last job, if you want to see them," they would say "absolutely not, please get rid of them RIGHT NOW," and probably fire me.
It's people who hold these beliefs who commit these acts. They're so convinced everyone around them is depraved, usually–at least in part–through personal experience, that they don't stop to consider the alternative.
But, I don't work in Silicon Valley.