In neal stephensons 1996 classic wired article Mother Earth Mother Board theres a bit in there about why cables are not attacked.
"There is also the obvious threat of sabotage by a hostile government, but, surprisingly, this almost never happens. When cypherpunk Doug Barnes was researching his Caribbean project, he spent some time looking into this, because it was exactly the kind of threat he was worried about in the case of a data haven. Somewhat to his own surprise and relief, he concluded that it simply wasn’t going to happen. “Cutting a submarine cable,” Barnes says, “is like starting a nuclear war. It’s easy to do, the results are devastating, and as soon as one country does it, all of the others will retaliate."
This rule was broken last year and it will happen again with more and more frequency.