Why I think rancher is something to roll with when doing things on on prem environments?
When one wants to juggle various services and containers one few years ago had little but few alternatives. They all looked like really good but once you actually try them on its like you get failure here or there and it will take time to get them up and running without trouble. While there were various systems to get your on prem services behave like in some cloud environment without deploying private cloud they were still while I was trying them not working out of the box often.
Deploying private clouds is a beast of its own and if one wants to avoid that while having next best thing to me it seems rancher is one of top things.
When having something to manage with docker no matter how good commands like swarm and other similar things are, having something more is for sure better.
With rancher although it comes with full kubernetes cluster one also get plenty of management features on top of docker. So even if rancher would be used for solely docker management it would be good at this point.
Having options to easily setup logging, rollback deployments, get shell from web gui it is just too convenient. It might sound weird but to me when one has to make something happen there is big difference between having to do stuff quickly or having to fiddle with swarm deployment and make it a quick work.
Rancher lets one have some of that private cloud feel and microservice management stuff without having to actually deploy private cloud or buy some top microservice management services that you have to integrate in your stuff anyway.
Although today there might be some competition that I did not yet explore to me it seems that if someone wants to have some docker containers juggled and some services without deploying private cloud on prem, Rancher might give best performance when it comes to cost of setting up and how much flexibility one gets.
One can get few services deployed, getting load balancer in front, getting logging done, monitoring, etc all very quickly. One can also automate a lot of stuff here.
So between choosing some alternative tool that will do similar thing for you, deploying private cloud, or trying to manage docker without anything, rancher seems positioned in the middle that gives a lot of leverage to a developer.