You might ask me, why would you, a modern guitarist learn to play by sheet music. It is an old standard that people who play classical music use. I agree, but at the same time it is a very useful tool. Reading sheet music allows you to access an enormous library of music written throughout time. Additionally, and honestly more importantly, it lets you communicate musically with other musicians more accurately. Sheet music is quick, honest and accurate; therefore, it is almost always a requirement for session musician jobs.