I've seen a few that do that, actually. Like a media keyboard with buttons for music controls, there are some that have additional functions like copy, paste, cut, double space, double enter, etc.

Now that you've said it, it does seem like an obvious improvement.

It's true they would probably be more useful to the average keyboard user than say the scroll lock key, or the fucking copilot key. But to be really useful, they would have to be easily accessible without moving you bands, or else it'd just be faster to use a shortcut. Keyboards with macro keys do exist so maybe get one and map them to CTRL+C/V

Do them 100000 times and see how comfortable they feel

Some keyboards have media keys for that. Some user environments also allow you to remap those keys to other functions.

My keyboard has a column of configurable macro keys. My last one had two columns. I use them soooo much I have literally never bothered to figure out how to set them up on this one.

Mech keyboard nerds are laughing in QMK...

Barring that, for Windows there's Auto-Hotkeys or MKLC (Win10)/Keyboard Manager (Win11). For Linux, I use Input Remapper for remapping mouse keys, but it works for keyboards too.

Seems like it would be more useful macro'd to extra mouse buttons.

Keyboard only people are plenty comfortable with frequent shortcuts.

Get a VIA or QMK customizable keeb and you can make any key into any key you want.

I have a mouse with programmable (ish) keys and I have some buttons assigned to copy paste. I like it.

Some of us... Do.