Docker seems to have gained more ground than LXC

They aren’t really competing in the same space. LXC is more comparable to jails or openvz in that they provide an os layer, Docker does not.

I recently saw docker described in a web comic where some poor dev was bemoaning that his software “worked on his machine”, and his teacher says “then we’ll ship your machine”, meaning Docker sets up a software environment for a project to work, nothing more.

Docker was at first based on lxc, but has since moved to its own libcontainer.