First, there are many people who don't want to publish their prices and menu on the internet for various reasons. 
Second, there is a problem of copyright with respect to printed menus: Often the creator / designer of them has a copyright that doesn't allow further copies or reproductions of the work, like with any other printed material.

Third, if the owner wants to have his menu published, they likely put it on their web page. Then we can just add a link using website:menu=* 