Tab notation doesn't provide full time signature information, if you're picking up a piece of music which you've never heard played before
In tablature, imagine one string's line shows ---10-----7--8------11----13. How long do you hold each note? Clearly 7 to 8 is quick, but how quick? Sheet music gives you this exact information.
That's a solved problem. Tab + stave notation, with the stave above and tab below.
There are some settings where it's good for a guitar player to be able to sight read. If you're playing for random bands, or playing classical, it can be a big help.
standard notation is much better for learning to see and hear patterns too.