There are many bakers who use a cookie scoop to ensure that their cookies come out to be the exact same size with each batch they bake. For a professional baker, the tool can be helpful because it guarantees that they will get the exact number of cookies that they need from a batch of dough. For a home baker, it simply means that baking times will be standardized and the finished cookies will all be evenly done.
But because some find the useful, it doesn't mean that scoops are necessary objects. I don't like using cookie scoops at home, despite the fact I have several different kinds. I don't find that they work well, even when I use warm water to rinse them between every few scoops, because dough will inevitably stick to them. I get results that are just as good - evenly portioned and evenly baked - when I simply "eyeball" the sizes of my cookie dough balls.
Scoops are a great idea for kids, though. They have a hard time measuring out the dough by eye and will end up with cookie dough in fewer places (hair, clothing, etc), if their hands aren't directly touching the dough. There is an added bonus of your child having their very own "special" tool in the kitchen, which will probably encourage them to come in and help out more often.
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