A conversation with my 7-year-old son at breakfast has made my mind up about the grammar ‘McNuggets’ debate. An epiphany over a potato farl.
Kai: There aren't really lines in space, are there?
Kai: Then why do they put them there in books?
The lines allow us to understand the orbit of the planets, the forces of gravity or the spin of electrons in an atom. Personally, I appreciate them. Explicit grammar presentation in language textbooks plays the same role. It's a big old cosmos out there.