And you can learn to converse in a society without being able to read or write, but just be able to talk to people. Would you feel comfortable going through your life as an illiterate in your native language? How do you learn a new piece by yourself if you don't have someone to play it for you? If you can't read notes, then you're useless unless you have another source to play it for you first. That's acting very dependent, and a selfish approach to learning to be a decent musician.
In the theory of music, there are certain rules. Rights and wrong. A D Major Tertian Triad is spelled D F# A, for example. Very clear-cut things. However, it's an art-form, so there are rules to be broken. However if you know notational rules that are standards the world over in music theory, you can read like an accomplished musician, rather than an amateur that has to count his/her lines and spaces for every single note.
Also, I'm glad you have mentors and colleagues, but there are some students that are self-taught and may not have access to such a variety of sources. It's nice to see that you don't need this section, but I think it's a little bigoted to say that everyone should go look for other sources of information rather than be able to come here, a MUSIC forum, and learn something too, rather than just gossip about the latest hit singles.