pull vs push. Plus if you start storing the last timestamp so you only select the delta and if you start sharding your db and dealing with complexities of having different time on different tables/replication issues it quickly becomes evident that Kafka is better in this regard.
But yeah, for a lot of implementations you don't need streaming. But for pull based apps you design your architecture differently, some things are a lot easier than it is with DB, some things are harder.
A Kafka consumer does a lot of work coordinating distributed clients in a group, managing the current offset, balancing the readers across partitions, etc which is native broker functionality. Saying you can replace it all with a simple JDBC client or something isn't true (if you need that stuff!)
But yeah, for a lot of implementations you don't need streaming. But for pull based apps you design your architecture differently, some things are a lot easier than it is with DB, some things are harder.