The ribbon (particularly in Microsoft Office) solves the problem that users don't know what they want, because it lays out all the options in front of them in a clearly organized hierarchy, with hover previews and textual labels for every command except for extremely well-known commands (like Bold/Italic). This is very different from chat interfaces, which are opaque black boxes and in order to get anything out of them users have to express their wish in words, with nothing to start from.