Why do Gums recede?

The answer is because there is a very close relationship between the tooth and the gum. They talk to each other. The gums talk to the teeth, the teeth talk to the gums and also to the bones, and there's a big interplay between all of those tissues, which has what's called a 'trophic' or growth promoting effect. And so, if you loose teeth, you also loose bone and gums, and vice versa. So, it's because one thing is there to protect and support the other. And if you take one away, the other one realizes that its role is now a bit more redundant. So, the gums thin.