There may come a point where they decide they need to do that. As it stands, it appears that they believe they can get the necessary level of security without physical air-gapping, which is likely substantially more costly (especially in terms of iteration speed).

Well heaven forbid their iteration speed takes a hit!

I do not have much faith in what they believe about their ability to enforce a security boundary given their track record so far, not to mention their grossly inflated sense of importance (both about their work and about themselves).