There is a video of a girl on youtube. She studied classical piano for years and at some point decided to learn popular music. It showed her transcribing Oscar Peterson solos and then playing them and her years of study allowed her to do that. So, I think for a piano player, it is really good to have lessons because that gives you the facility to play anything provided you practice long enough. Then, if you know theory as well you have the whole package.

I don't think note-reading is as vital for a guitar player but a basic understanding of theory is a good thing for anybody. That said I have a basic understanding of theory but never read music and never took lessons. I just fool around with an arranger for enjoyment.