Folks can design images in WYSIWYG tools like Photoshop because the output standards are much more stable and consistently implemented than HTML + CSS + JS. Every OS, browser, image viewer, etc. will render a JPG, GIF, or PNG almost exactly the same. But give them all the same HTML, CSS, and JS, and you might get very different results--especially if you are trying to make use of the coolest new features. Basically, hand-coding is the price we all pay for an industry that is innovating its technology so quickly.