We are now in the age of components where we build self contained parts of our application in isolation and then wire them up later in various parts of our app. For this reason, adding margin to our components is considered harmful. In this age of components, there is a big need to abstract layout into its own component, using React's powerful composition pattern to layout our components for us in an easy and consistant way.
I have worked on two internal only design systems. Neither one of them were given permission to be made open source. Ultimately, I decided to build this library so I could take advantage of the things I have learned about building Layout components so I can reuse them in my own projects.
As I mentioned before I have worked on two internal design systems, but I would have to say the resource that has inspired me the most has got to be every-layout.dev. This resource is fantastic and worth the $100 dollars for the time and energy they have spent making it.