Why are default values written to the config file?

[thallgren]

When the config file is written out, the default values are written out too. Thus, the fact that they represent defaults, and hence can be overridden, is lost. This means that a binary where a default is modified (say, by an upgrade), will no longer get its default although no one ever added the value to the config.

So my question is, why are default values written out? If the config is written, I end up in a situation where this doc from SetDefault is no longer true:

// Default only used when no value is provided by the user via flag, config or ENV.