It is because it is the foundation for the mathematics underpinning your question about communications systems, encodings, and their various structures. It also explains why the choice of the log likelihood is a better fit for estimating a token-based model than some other hand-crafted heuristic.

The version with the Weaver introduction is quite good as well, there are other versions of similar papers covering the topic from different angles, I find it to be well-worth the read.