Is Sub Minute Latency Really Just a Problem for a Certain Subset of Companies?

Real time API's are almost like a streaming ETL if you will, right? Like what you would traditionally load in batch. You're now loading essentially in real time with sub minute latency to some sort of data store downstream. Do you think that these will get super wide market adoption or is it really only a problem for a certain subset of companies? Or actually I have a third flavor: Why not stream in real time if you can, because it's cheap.