I believe that is actually what tab is for. There are many of the same notes that can be played at different locations on the neck. Tab is one way of showing you where to play the notes. Thats why there is no info on rhythm or timing, it was never meant for exclusive use for writting down songs or sightreading. It is an aid in reading standard notation.
I believe one of the reasons for its surprising popularity is the fact that it is so easy to write on the internet, just lines and numbers. I always thought it would be cool if there was a typing program that allowed you to do standard notation over the web or something.