There is no exclusively visual side of things for web design. Sure you do the initial design in Photoshop but once you need to add interactivity it's no longer

There is no exclusively visual side of things for web design. Sure you do the initial design in Photoshop but once you need to add interactivity it's no longer purely visual. You've sliced it up and you can't put it back together. Xcode works because even on mobile/desktop there is more separation between design and functionality than the web. The web is both more primitive and more flexible.