> Dozens of times a day I add someone to the cc list

Incidentally, your daily dosage coincides with the amount of times I've had to do the same thing at all since I started using email some twenty five years ago.

> It's an incredibly common use case

For some, perhaps. On the other hand, I'd suggest that another, at least for me more common use case is to know exactly what is being replied to. Which is possible with proper quoting, rather than the let's-just-slap-on-your-entire-message-at-the-bottom-and-hope-you're-a-mind-reader nonsense.