In the US there are quite a few landings just outside of NYC and LA. I'd guess London is too far inland, and it's cheaper to run fiber over land. There is prob

In the US there are quite a few landings just outside of NYC and LA. I'd guess London is too far inland, and it's cheaper to run fiber over land. There is probably also an incentive to keep the cables away from major shipping lanes where they'd disrupt the ability for ships dropping anchor. Notice around Seattle some cables snake up and through the sound, but it's also extremely deep water. That landing is also far north of the city proper, so any ships waiting near port are a ways from the landing site.