Use Cases and Deployment Scope
We have a video conferencing and live streaming product. The live streaming product is built on HLS but it can take can RTMP-in feed as well as output RTMP if needed to external providers. We, as well as a lot of our customers, use OBS Studio for sending the RTMP feed to our live streaming product. This is primarily because OBS Studio is a lot more extensible and has support for multiple devices, mics, cameras as well as combining of different feeds.
Alternatives Considered
StreamYard, Restream and Streamlabs