I mean we were doing that way back in the day, the only trouble with that approach is that, like I mention in the article, bitmap/raster image data scales like crap, and unless we feel like doing 9-slice scaling on buttons (which comes with its own set of problems), you'd have to redo each one every time you changed the content, and that's not even touching on the accessibility issues an approach like that could cause.

The nice part about using modern tooling with morphic styles is that we no longer have to sacrifice a large degree of aesthetic qualities for accessibility or scalability because SVG and CSS scales seamlessly across devices and browsers, all re-rendering as-needed, on the fly, and looking sharp doing it.

Now granted there are certain aesthetic qualities that are sacrificed, namely difficult to reproduce metallic finishes or anything with complex, layered highlighting, but the fact remains that with modern tooling we're finally able to get away from the issues with bitmap that we just couldn't get around well in the past which made these aesthetics obsolete in the first place.