I'm pretty sure that the map doesn't actually show the correct paths, just the schematic "A connects to B" sort of thing. Laying cable is expensive, but so is fixing it, especially undersea. If I were laying cable I would try to keep the undersea runs reasonably short, especially if I need repeater stations. A Canada-Greenland-Iceland-Faeroe-Scotland link runs 2500ish subsea miles with several hauling-out points, while a direct New York to England route is more on the order of 3300 miles with no hauling out point (3700 with a stopover in the Azores).