"Did they ever stop and think that their employees want to go somewhere to get away from the the Apple environment so they can unwind and relax?"
In which case they are going somewhere, perhaps without other Apple employees, where they won't be discussing anything that may be a secret. So feel free to go anywhere you'd like for non-work related conversation and stick to 'internal' locations where such things will or might be discussed.
Granted, I think the easier answer is to close off the current cafeteria to non-Apple employees than to open a whole new place.
I used to work for a company a couple of blocks from Apple headquarters; our cafeteria was technically open to the public, but the building required card access, so the average guy off the street couldn't go [without knowing someone internally or sneaking in I guess].
We used to go next door to Sun's cafeteria which was open to anyone [though it cost more for non-Sun employees to eat there]. I'm sure Oracle, Symantec and others also had cafeterias, but I think they were more like ours, where you first need access to a 'secure' building [granted, I could and did get into our 'secure' building with a coat hanger

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