They don't need to be leaf components to still have this strength. I've worked with design systems which have a <my-layout> component near the root which defines sidebar, header etc slots. This still works nicely with react, Vue etc
But I agree they tend to be better suited as "leafier" components
> I've worked with design systems which have a <my-layout> component near the root which defines sidebar, header etc slots.
Funnily enough this is exactly what original proposal of web components was against :)