The Jungle Book is a little misleading. Out of the book's fourteen chapters, ten take place in the jungle, but the others don't. Kotick the seal would be pretty out of place in the jungle, and his adventures take place in the Bering Sea. And the final two chapters take place in a military camp near Rawalpindi, in what is now Pakistan.
So The Mostly-Jungle Book or The Jungle, Sea, and Pakistan Book aren't as catchy as simply The Jungle Book. And aside from trees and gigantic insects, you most likely think of animals when you think of the jungle, and animals are what tie all of the stories together.