If all they eat is chick starter, no, they do not need grit. If you also feed them boiled eggs or yogurt, no, they do not need grit. If you feed them anything that needs to be ground up, like grass, grain, or many bugs, yes they need grit.
Do they need it every day. Not really. Grit stays in the gizzard until it is ground up so tiny that it passes on through their digestive system. How long grit lasts depends on how hard it is and how big the bits are to start with. I keep it available most of the time, but I don't give them enough that they will fill up with grit instead of their food.
If they are foraging, they are probably getting all the grit they need. There may be some exceptions, such as they are foraging on swamp muck that is nothing but tiny particles of dirt, but they are almost always successful at finding something to use as grit.
I like to give mine grit from about day 3, as soon as they have figured out what their main food is. I don't give them a huge amount, but enough to get their system started the way it was meant to be. I think it may (or may not) help prevent pasty butt, but they are prepared in case they eat something they need to grind up, such as wood shavings or maybe if a bug wanders in their brooder.