Presumably written by someone without much interactive shell experience.

When you're building a pipeline, putting cat first can often be quite convenient. Essentially, it's more composable: it defines the input to the pipeline without committing to a specific tool. For example, you can up-arrow in the shell and change the part after the pipe without having to skip back past the filename.

In fact if you don't start with cat, it's possible you're more of a script kiddie than a software developer.