I agree with what you're saying if a person takes the orginal tab-book and duplicates it to share with others, but what if it's just a fan's interpretation of how a song should be played leh? Key word is interpretation, most of these tabbers make that very clear, and do not pretend that the tabs they put out are the OFFICAL, ACCURATE version.
everyone who uses online tabs understands this, and will go to the appropriate sources if they want the official tab.