Well, the 2001 PowerBook is still an iconic design. It’s just like saying why make macOS look like System 1 by having a menu bar or NeXTStep by having a Dock. The amazing thing about the Apple platform is it’s lineage and consistency. Taking some design cues from previous products is nothing bad. Look at the iPhone 12/13, they both share a similarity to the iPhone 4/5. Remember those old products were designed by Jony, too.
David Pogue explained some of the design reasons for the Notch:
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But, I think Apple is planning on other investments in the Notch on the Mac, obviously Face ID. They are a business too, which means, they are gonna make the second generation the same size with Face ID to get you to upgrade. In 2023, they will make it smaller like how they made the notch smaller on the iPhone 13 to get you to upgrade to each iteration.
I also think we are gonna see Touch come to the Mac in maybe a few generations, so the size is likely training the mind and slowly get app devs to mod their apps for when that happens. Apple knows so many of users are exposed to its platforms through its touch first devices (iPhone and iPad). And it someways puts the Mac at a disadvantage of not having some rudimentary touch capability built in even its just for the ported iPad apps that would still benefit from it. But what I suspect will happen is they are gonna radically change design of the Menu bar probably in the next version of macOS. Likely it will be split off into two different sections for file menus and status.