system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Does mixing ingredients separately actually affect how the end product turns out? If so, how?

I was baking Christmas cookies and I realized that it always has you mix ingredients separately, and then blend them all together. Why is this? If you're just mixing them all together in the end anyway then what difference does it make?
gpt
It's because the order and method you mix things can have a huge effect on the outcome. For example, let's take the most common mixing method, the creaming method: 

First you cream together the butter and sugar, because the sugar punches microscopic holes in the butter that aid in leavening. Any additional ingredients at this stage would inhibit that. Then you slowly add the eggs, just a few at a time, because eggs have a lot of structure and take time to get fully incorporated. You sift all of your dry ingredients together because powders like to clump up, and once those clumps get wet they're much harder to break up. You add your dry batch last to minimize gluten development, because any mixing after the flour is added will create gluten and could make your product tough. If you have additional wet ingredients, you alternate adding portions of your wet batch with portions of your dry batch to allow the flour time to soak up the added moisture.

If you were to take all the ingredients of a butter cake and just toss them in a mixer, you would end up with a lumpy brick. If you follow that method, you'll get a tender, airy cake with a consistent crumb.