I once thought the same thing, but after months of studying our music system and our way of notating it, I came to understand why it's so difficult to improve upon staff notation.

First of all, Western music has complex structure both horizontally and vertically. This makes it rather difficult to encode and visualize, right at the outset. You need some sort of matrix visualization, like a staff or piano roll, to capture all of the nuance.

What makes the staff so useful is that it also captures the tonal aspects of music in compact way -- those that relate to the key the music is written in. Every triad in the same inversion looks the same in every key. A triad is three consecutive lines or spaces. And then deviations from the standard triad for that tonal function are marked with accidentals.

This turns out to be extremely useful for performers, because you learn to play an instrument by learning to play in all the keys, rather than learning what the 12 notes are and playing note by note. I realized this when taking piano class and doing exercises where we'd transpose to another key while sightreading in the original key.

There are other notation systems that have been as successful as the staff, but they tend to be specific to particular instruments or styles. For example, most guitarists find tablature much easier to play than standard notation, especially if the tablature is augmented with note durations and rests.

Also, although I've become a true believer when it comes to the staff, I have less rationale for why the traditional clef system has stuck around. It seems like something that is more regular as you go up and down the scale would be more helpful. There are systems that use things like note shapes or colors to help mark the note name. I guess we just haven't found a standard.