I think you’re fighting the hypothetical. Suppose this magic system requires the use of book items for reasons - the character can’t memorize the spells, or maybe the magic only works when read from a page. As soon as you put down the book you can’t cast spells any more, and the actions only work when holding a speedbook.
Here’s another example. A mod adds a new multitool, a swiss army knife. This mod adds a new action for each of the multitool’s “modes”, that is, for each tool that swivels out of the knife. Do you expect the swiss army knife to be useless until the player goes into the keybinding menu and sets up key bindings for each function of the swiss army knife?