If you have N things producing data, and M things consuming data, you have a problem where each of the M consumers needs to handle all N types of input data, meaning you have to implement N*M things. But if you have a "narrow waste", meaning a common interface like JSON that all N things are capable of producing and all M things are capable of consuming, then you only need to implement N+M things (N things that produce JSON, and M things that consume JSON).