You just weigh the egg you're going to use.
Just think about how annoying measuring a cup of peanut butter is, scraping it out of the measuring cup, washing the cup.. vs just adding spoonfuls of peanut butter to a mixing bowl.
You can still bake just fine with measuring spoons and cups but you’ll be more consistent and better with the scale.
They are required for experiments. I like to add a small amount of baking soda into my banana bread for a nicer crust but if you add too much, think 0.X grams too much, then the banana bread could begin to have a vaguely pretzel-like taste.
Just buy one.