If I sit down to play a page of notation, I don't need to know the piece I am playing. The note names, length, timing, tempo etc is all on the music, it can be played as is.
With Tab you need to know the music to be able to play it, you probably need a recording to get timings etc.
If you put a sheet of notation in front of me, even a new never played before item of music, I can play it. You can't do this with a copy of Tab.