When reading about linking containers together they now call it legacy links e.g. here.
This article claims links
got deprecated in Docker 1.9, but the release notes doesn't mention this and the list of deprecated features doesn't mention it either.
Question
Why does Docker now call links
for legacy links? And should I stop use them?
Docker networking is being promoted as successor - https://docs.docker.com/engine/userguide/networking/
On whether you should stop using them - yes. The docker world is currently moving very fast, and links has been "legacy" for a few releases now.
well at least mentioned here by Docker official documentation:
https://docs.docker.com/engine/userguide/networking/default_network/dockerlinks/