But they can do this today, while the majority of people continue to use the integrated "dinky DAC" (which is actually quite good in case of the iPhone).You don't need a great DAC for phone calls. Even HD audio calls can have a dinky DAC. But you are very limited by how great a DAC you can build into a phone. Size and cost constraints are huge. If you externalize it, the user basically can choose how good a DAC they want by choosing higher-end headphones.