ExplanationSNMP polling can often be in the order of 5-10 minutes, CLIs are unstructured and prone to change which can often break scripts.The traditional use of the pull model, where the client requests data from the network does not scale when what you want is near real-time data.Moreover, in some use cases, there is the need to be notified only when some data changes, like interfaces status, protocol neighbors change etc.Model-Driven Telemetry is a new approach for network monitoring in which data is streamed from network devices continuously using a push model and provides near real-time access to operational statistics.
Referfence: https://developer.cisco.com/docs/ios-xe/#!streaming-telemetry-quick-start-guide/streaming telemetry