When creating a bundle, it is useful to configure it, which will be used as a library (and not only).
Of course, you can put everything in parameters, thus avoiding configuration, but that would not be kosher. =)
Proper practice is to describe the configuration in config.yml, and to extract some necessary parameters into parameters.yml:
Recently, I discovered for myself that apart from writing code and learning new technologies/using external APIs, there are things that are much more challenging.
These are things that need to be understood when developing medium to large projects. But even for relatively small projects, this is important.