So, if we could induce those brain waves we wouldn't need sleep? Maybe in the future our AirPods will have a "rejuvenate" feature which plays tones that cause sleep like brain waves to go through and clean out our neurons.

Probably not... I think our brains are like LLMs. We train them on sensory input we perceive over time, building up a data model that is unique to us. The models may generate similar results, but each person's brains are wired as differently as the raw binary data stored in ChatGPT vs Llama or Gemini. Thus the cleaning mechanism is probably unique per person as well.

But I don't really have a clue. It's just a logical inference.