Just like many projects care about different aspects of tracing, different groups of people are their target audience:
Tracing system authors care about recording, federating, and correlating transactions, and about the projects attempting to standardize data formats for trace data and for metadata.
Tool users, for example, DevOps, SREs, and application developers, generally only care that the tool works and helps them to analyze transactions. They are not involved in most projects around the standardization efforts.
Data recorders, which often, but not always, include tracing system authors, care about recording transactions and work on tools that may include tracing libraries. For example, the OpenCensus project is focused on data recording, but it is explicitly agnostic to the actual tracing backend that receives the data. It is not maintained by the same people who maintain the tracing backends.
Application developers care about instrumentation APIs that help them to describe...