Do I need to learn music theory to become proficient with Guitar?

I was reading an article in a Guitar method book that recommended learning music theory to be a better guitar player. Clearly the implication was you need music theory before you make the jump from playing guitar to Playing Guitar with proficiency. I took years of Piano lessons as a child but never learned ‘theory’. I learned how to read music and play the notes on the page. I can still play Piano music if the music is there, but cannot improvise. Is my lack of theory education the reason I can’t just sit down and plunk out a tune? And will this also affect my Guitar playing in being able to play the instrument without a chord chart?