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.
I work for a Silicon Valley headquartered company and would expect the same.
Companies don't get to be worth billions of dollars without doing something unethical.
I had the opposite issue, I once got criticised for not bringing client information with me.