Start by asking the users and managers of the large legacy system, “what are your pain points?” Typically you’ll find that the pains have nothing to do with the ability to deploy quickly or start up lots of little containers in different places.
These large legacy systems are rarely installed from scratch, and have all kinds of complex setup configurations that we’re done by outside consultants or vendor employees. Folks may not even know what it would take to rebuild and redeploy the system from scratch. There’s no ROI for the company to take risks by redeploying it in a different way.
It’s like asking, “Drones are awesome. Why don’t train companies switch over to them?” You have to first understand the problems that train companies need to solve. If you really wanna get drones into that market space, you don’t talk to the train companies: you talk to the train customer’s companies, find THEIR pain points, and use new technologies to win the customers over.
That’s exactly what containers are doing: they’re being used by brand new apps that disrupt legacy systems.