Nobody thinks you "need" it, but staples are cheap, easy, shelf-stable, unrefrigerated, and at least appear healthy.

If we're going to feed billions of people, it's probably going to involve staples.

I know I don't need it. The problem is it is hard to avoid it. You need a lot of planning, specially if you are going on a trip (at least in my country, avoiding flour while traveling through small towns is almost impossible if you want to have eat health)