Self-teaching has nothing to do with whether or not you learn theory. You can bone up on theory without a teacher to explain it to you. As far as whether to learn it or not, I like what Victor Wooten said in reply to a question about it in the Live at Bassday 98 video; music is a language. When you speak a sentence, you don't think about the grammar much. You KNOW the grammar, whether by having been taught it in school or just by having absorbed it from other speakers of the language, but you don't consciously think about it while you're playing. Music is the same way. You should KNOW the grammar of music - the theory - whether from formal study or by absorbing it from other musicians. But by the time you play, you say what you want to say in your music. The grammar fades into the substructure.
Anyway, to the OP, I was certainly of the impression that many if not most of the great classic rock bassists of the 60s and 70s were largely self-taught, at least on bass. Some may have had lessons on guitar and then switched over. Entwhistle was a French Horn player or something before taking up bass, I don't think he had a bass teacher. Chris Squire learned music as a choirboy. Same is true in later eras: I think all the guys in U2 except Larry Mullen had to figure out their instruments on their own. There are lots of examples.
EDIT: the "orchestra" comment puzzles me. Seems to me that an orchestra setting, where you're given sheet music to play, is where you need to know theory the LEAST. There's no playing by ear, no improvising, no ad libbed fills. I once had a performance where we had this weird little combo to supply music under a program of teen girls reading their poetry. We had me, a guitarist, a harpist and two flutes. When we had rehearsal and heard the poetry, the guitarist, the harpist and me jumped in and started jamming. The flautists, who were from the local civic orchestra, said "let's go home and find some sheet music to match this." We couldn't tell them "let's do a jam on this in D minor," they had no idea what to do.