> Why not just have an image of a menu and a box where you type the order.
Because then the menu wouldn't be readable, searchable, or adaptable by many people, including blind, low vision or dyslexic users. Meanwhile, the people who could read it could type any old freeform nonsense into the box... nobody has to care about spelling on a phonecall or proper ordering system.
Also assumes that people will type useful instructions and not "I want two of the pizzas with the red stuff", failing to note size, crust type, or what the "red stuff" they are referring to is.
Because then the menu wouldn't be readable, searchable, or adaptable by many people, including blind, low vision or dyslexic users. Meanwhile, the people who could read it could type any old freeform nonsense into the box... nobody has to care about spelling on a phonecall or proper ordering system.