In my experience :
Some complications on kubernetes are just inherent to a google-ish state of mind. If you're not on GCE, then you have to implement an overlay network, which is basically a fatass iBGP AS with a spoon of iptables.
Since your can rely on the linux kernel to ensure a proper set of routes, you do NOT need an external db as a dependency.
Tl;dr : I think the use of etcd in a network infrastructure, even SDN, is quite useless in most of use cases and understand the underlying nature of an overlay network is more important than just reproducing a basic tutorial entitled "how to prod kubernetes in 5mins". More to follow on this subject, I've left a half written blogpost in my company's drafts