One possibility is Mnemonics. You were memorizing the important letters in a text-based menu. Possibly even the keyboard shortcut mnemonics themselves. That's said to be one of the biggest losses in Windows user experience that keyboard mnemonics used to be highlighted at all times with an underline in text menus and then Windows UX switched to only highlighting them when Alt was pressed.
It's something I think about a lot with the Ribbon because it has some really good keyboard mnemonics in Office applications, but mostly only Power Users think to press the Alt button to let them "bubble in" on the Ribbon. The keyboard mnemonic bubbles make great landmarks, and I think that remains one of the reasons I rather like the Ribbon (as a power user) that a lot of people never discover. (In part because I was there a million years ago when Word first lost the underlines and was used to even then pressing Alt on its own just to see them so that behavior carried over to the Ribbon just fine for me, luckily enough.)
It's something I think about a lot with the Ribbon because it has some really good keyboard mnemonics in Office applications, but mostly only Power Users think to press the Alt button to let them "bubble in" on the Ribbon. The keyboard mnemonic bubbles make great landmarks, and I think that remains one of the reasons I rather like the Ribbon (as a power user) that a lot of people never discover. (In part because I was there a million years ago when Word first lost the underlines and was used to even then pressing Alt on its own just to see them so that behavior carried over to the Ribbon just fine for me, luckily enough.)