It's used by subsystem maintainers to request Linus pull their changes (it is literally the only mechanism Linus accepts from subsystem maintainers, outside of

It's used by subsystem maintainers to request Linus pull their changes (it is literally the only mechanism Linus accepts from subsystem maintainers, outside of a few outliers like the -next tree). But yes, most regular developers don't use it -- it doesn't allow for inline patch-by-patch reviews like "git send-email" or "b4 send".