Well, if you're writing something the user will be looking at and clicking on, you will probably want to have some sort of state management that is global.

Or if you're writing something that seems really simple and it's own thing at first but then SURPRISE it is part of the system and a bunch of other programmers have incorporated it into their stuff and the business analyst is inquiring if you could make it configurable and also add a bunch of functionality.

I also had to work with a system where configurations for user space were done as libraries setting global constants. And then we changed it so everything had to be hastily redone so that suddenly every client didn't have the same config.