Google Fiber was infamous for doing it this way, called "microtrenching" or "nanotrenching", where they either cut a trench into pavement and lay the cable into that and fill over with asphalt or other material. When done poorly (read: most of the installs that they've done), it erodes the road surface and the base and causes all sorts of problems [0] [1] [2] [3]
Also lots of providers just string up cable on poles, which are routinely snagged by trucks, shot by ammunition, run into by cars, etc etc, so even more vulnerable than shallow burial. Some of these cables are major links so damage can cause wide-reaching problems. No match for an out of control sedan, let along a nuclear strike. [4] [5]