basically everyone uses Excel. And basically everyone is a MOUSE-first user (or, even further along the chain: TOUCHSCREEN-first)
keyboard-based menu navigation is not intuitive. it can be "poweruser" oriented, but it's not for most of the userbase
I'd be willing to bet that professional typists and people who spend the majority of their day typing (email, word, IDEs/text editors, etc.) are the ones who will know more keyboard shortcuts and navigation, especially for the things they do repeatedly.
I would say that it's true that the keyboard shortcuts for those items are the ones most likely for people to learn, but not true that most people will learn them.
I've spent 15 years in (tech support/programming for) academia, working with genuinely very smart people who use computers every day of their life, many of whom are actively looking for better ways to use those computers in their teaching and research, and 9/10 of them go to the Edit menu for Copy and Paste every. single. time.