For example:
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When you open a fresh jar of peanut butter do you only work through one side until it is completely empty then start on the other side?
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Or when you get those shallow tubs of hummus does it have to make it back home undisturbed? Then one of the baggers at the grocery store shoves it sideways into the bag completely ruining the symmetry.
But sides are made in consideration of the main course and are intended to be eaten/enjoyed together.
Why are side salads typically served before, and separate?
Because they are a separate course and not a side. They call it a side salad like Americans call the main dish an entree, we like to use words wrong.
Then the world is lawless chaos, and I can enjoy my meal one dish at a time.
Word meanings shift over 500 years, nobody is using “entree” wrong because it means different things in different cultures and has changed several times over the centuries. The way we serve and eat meals has also changed considerably.
https://languageoffood.blogspot.com/2009/08/entree.html?m=1
I like this write-up, it had plenty of historical examples.