Not as rare as one might think.Ha! I was waiting for someone to point this out! It's rare, though, that they never eat anything else, like grass or bugs.
Like many other people I know, my chicks and growing stock are not fed any "treats" their sole diet is their feed so there is no need for grit. My free range/ pasture raised birds have access to natural/ native soil so, they get all the grit they may need. Now my layers, breeder and show stock are the only birds that I offer supplemental grit to because they're in their pens 24/7 and I do offer a mixed grain supplement along with their feed.
If I wasn't offering a grain mix supplement to my layers, breeders and show stock then they wouldn't be getting a grit.