For the same reason why the shortcut for copying a password from the slide-to-reveal menu on the iOS list-view for logins, I think that having the ability to easily copy the one-time passwords from this menu would save a lot of time, especially when you have a bunch of information separating the one-time password field from everything else (forcing you to scroll down to see it). It becomes rather tedious to have to get that information manually rather than having it available to copy readily from the list-view.
I've seen this topic posted here a couple of years ago and saw that it was being considered, however I think that it should be high on the list from a usability standpoint. It's the only reason why I still use applications like Google Authenticator or Microsoft Authenticator--because they're just easier. Anything you can do to make it easier for people to invest in 2-factor authentication and remove the friction associated will only lead to better security for your customers and a better experience overall. I use 1Password 1st because of its security, and 2nd for its usability, and this improvement would be much appreciated.
1Password Version: 6.5.3
Extension Version: Not Provided
OS Version: 10.3
Sync Type: Dropbox