"Developers" (I use the term loosely) coming from e.g. React are getting used to storing data in a global state. The Redux library lets one change the value in the global state, and all places that use the value are updated "automatically" (e.g. by tons of behind-the-scenes code that the "developer" on his brand new mac doesn't notice, but users on five year old Windows machines with a dozen open tabs do notice). Vue has a similar implementation, Vuex.

When not using React or Vue, people used to these conventions will not know how to properly pass state between objects. This library is for them. It really offers little more than `window.pets.dog.species = "poodle"` would offer but because it is a library it feels "less hacky".