And it'd be harder still to convert billions of existing people to another layout. Inertia's hard to overcome, even if another keyboard layout or music notation system had ever been convincingly proven superior than the respective dominant ones.

"In order to avoid jams" is a popular story but it's credibility has been challenged [1]. It may be worth noted that Qwerty was made before people used all fingers and touch-typed---they were likely to use just two fingers and typing speed might be quite slow in today's standard.

[1] http://gizmodo.com/qwertys-origin-story-is-a-big-fat-lie-493... (This is just a first one I found in English, but Prof. Yasuoka referred in the article publishes quite a few articles about early typewriters in Japanese, in which he lists several evidences that "jamming" wasn't the reason.)