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.
But, I don't work in Silicon Valley.
Companies don't get to be worth billions of dollars without doing something unethical.
I work for a Silicon Valley headquartered company and would expect the same.