One of the best resources to understand "why would I not ... ?" in a data intensive context is Kleppmann's Designing Data-Intensive Applications[1] (mentioned elsewhere in the comments). There's a lot of nuance to why event streaming wins out over periodically "polling" a database, mostly about maintaining correctness while being able to scale horizontally.

Taking a look at the Kafka docs [2] is also enlightening.

[1] https://www.amazon.com/Designing-Data-Intensive-Applications...

[2] https://kafka.apache.org/documentation/#gettingStarted