I think alot of you misunderstood what I was saying...
I said "decided" as sort of tongue-in-cheek. I'm well aware that our current system developed slowly over hundreds of years. But there was still a "decision". Musicians have collectively decided, probably by default rather than conscious action, that not changing is easier than coming up w/ a new system. The system is "good enough" for what we need and it would be "expensive" to replace. It is expressive and it works, but that doesn't make it perfect. There just isn't enough pressure to improve. Similar to evolution. We could have evolved better eyesight that extends past infrared and ultraviolet, but our eyesight has served us well enough to avoid being killed, so there's not enough evolutionary advantage to a wider spectrum.
And on the rhythmic notation, it's the same. It works. It expresses our intent well enough and is fairly entrenched. But again, that doesn't make it perfect.
Written music is similar to a written language. Not everyone can read or write English. So, once upon a time, someone invented Esperanto. A very logical language that is relatively easy to learn. But it hasn't ever been widely accepted because it requires everyone to change to something unknown. If I were to move to Germany, it's much easier for me to learn German rather than make all Germans and me learn Esperanto. Similarly, many musicians read the current standard system of music and do quite well with it. Learning that system is much easier than trying to invent something new and get other muscians(who already have an accepted language) to adopt it.
Once again, I'm not saying that it doesn't work, or even that I have a solution that is in any way better. I'm just staying what we have is not perfect.