Why would it want to? I'd say what you're asking for is actually a code smell. An app should not have a bazillion interlocking ways to be configured, unless there's a strong reason for this!
It's not the app, it's the environment variables that have many ways to be configured.
> Why would it want to?
Because well behaved applications play nice with their host system.
I have a strong suspicion that you’re thinking about application configuration, not environment configuration.