They can but it's an involved process. Modern cables manage their slack very precisely - a complicated job in and of itself - and usually cannot be hauled to the surface without snapping them. So if the cable is not already cut (an anchor can damage a cable in a variety of ways short of physically snapping it) it will be cut while still on the bottom. The ends are then winched up and a splice is patched in but now there's a rather lengthy section of extra cable to deal with. They deal with that by laying it down precisely on the seabed in a nice sideways loop.