Showing a page of code do your wife is one thing, but stealing source code files is a complete other. Orgs are installing tools to track what you do and when you do it so that they can audit your actions. They might not be able to prevent you stealing the code but the evidence of your actions will be usable in a court of law when they make an example of you.
If you have never worked in a highly regulated industry such as defense or finance then I don’t think you would be so flippant over the data loss concerns.
I work in finance; if you came to me with these sorts of concerns I'd think you a paranoid lunatic.
Lock your screen when away from your desk, but no one is going to be pulling the secret sauce from your systems by occasionally going into your office to ask if you'd like a cuppa.
