The concept of network automation has been around for as long as there have been networks, and until now the uptake has been slow for a number of reasons including resistance from network engineers. But now forces are coming together to create a perfect storm of sorts, driving a need for network automation tools.
One factor is that more and more network teams are starting to feel the pain of working in the fast-paced digital world where doing things the old way simply does not work. The manual, box-by-box, method of configuring and updating routers and switches through a command-line interface (CLI) is too slow and error prone.
Also, the rise of software-defined networks (SDN), including software-defined WANs (SD-WAN), has enabled network-automation tools to evolve from operationally focused point products that address things like change management and configuration into policy and orchestration tools.
Thanks to Zeus Kerravala (see source)