Because there is no such seperation in natural language. Supposing I had a list of what to buy at the grocery store: 1. Eggs 2. Spam 3. Spam and Eggs 4. Never

Because there is no such seperation in natural language. Supposing I had a list of what to buy at the grocery store: 1. Eggs 2. Spam 3. Spam and Eggs 4. Never mind, let's not go to the grocery store, it's a very silly place. You made sense of that. Natural text is mixed in that way, and we want LLMs to be able to process exactly that kind of input.