Hacker News Reader

Many apps do have pinch to zoom on viewports. Just about any app that displays pictures, for example, or any app that displays large amounts of text.

That's true but those are scalable components within the app specifically designed to be scalable. You're not scaling the entire app window.

If you have an area you want to be scalable, you'll have to implement it in JavaScript or use a pre-made component.

I actually find myself wishing I could scale whole apps on mobile sometimes.