Because traditional WANs were never designed for the Cloud. Meanwhile, customer applications are hosted in:
– On-premise Data Centers
– Public or Private clouds
– SaaS solutions such as Salesforce.com, Workday, Office365, Box and Dropbox,..
Routing traffic traditionally from the network to the branch office to the main office, then out to the internet and back again takes time and increases latency. So the purpose of SD-WAN is to automatically route traffic, increase performance, and minimize latency so that customers can use the application most effectively.