Todo apps are used as front-end examples for the same reason the factorial function is used to explain recursion: it's simple, it's intuitive, but it exercises

Todo apps are used as front-end examples for the same reason the factorial function is used to explain recursion: it's simple, it's intuitive, but it exercises what you need without dragging in a lot of incidental complexity. To demo or teach a front-end framework, you need to show: 1. How data gets rendered to the DOM 2. How collections are handled 3. How events are registered and handled 4. How the DOM is updated when data are changed 5. How form inputs are represented The easiest thing to do is to show an array getting rendered as a list, then add click handlers which change the list somehow, which naturally segues into showing how the DOM is changed. Adding new items or deleting items also answer important questions about how exactly collections of data are mapped to collections of elements and how updates are happened. Finally, no demo of a front-end framework can be considered complete unless it addresses how form input elements work; adding functionality to add a new item or update the text of an existing item is an obvious way to demonstrate this.