I sprinkle chick grit on their food on day 1. That's because I feed them things other than 100% chick starter. They get bugs and worms from me as treats and to get them friendlier. If they're going to eat anything other than chick starter, yes, they need grit in moderation. I don't put out an entire bowl of grit because they don't know what food is at a young age... so I sprinkle it on their food like I was salting it.
When my chicks were really little they wouldn't eat any treats at all but if I gave them a dish of play sand they went crazy over it! Scratching and pecking like mad. They were so cute. If all you feed is chick starter you don't need it but it was way fun for mine.