I promised several friends here that I would, occasionally, chime in on pertinent topics, other than my selling my baroque flute. Great flute, BTW, for a good price.
And I also mentioned that, eavesdropping here and there, some topics just seem to stick around, as if I’d never left. This is one of them, but – well – here’s my two cents on it, yet again… as if I’d never left… 
Reading notes has little to do with traditional playing. Playing has little to do with literacy. But it helps with learning, for those that can do it, and that’s no small thing. Let me clarify with a non-music analogy.
Actors generally work with scripts, and have for centuries, although illiterate actors (or foreign born, with another language more fluent for them) probably still exist, and once upon a time, they were probably pretty common. They learned by memory. Bela Lagosi barely spoke English when he was cast as Dracula, and his quirky preformance and rhythms are largely due to phonetic memorization – he did not understand a large part of what he was saying.
But, while reading and memorizing have little to do with acting and performance, reading surely helps the process along for those that read. I learned some 300 tunes early on, long before these tunes were under my belt, by reading them and practicing them as I grew. My teacher, a traditional player of some repute, wrote them out for me (and his other students). Do I stick to the “script” now? Probably not, but they are nice settings - nicer than many heard in sessions - and they were the basis of my early ITM education. And most of these tunes – and many others by now – are well ingrained in my brain, fixed just as surely as any pop song or commercial jingle heard growing up. And fixed just as surely as the tunes I originally learned by ear.
My point? I guess playing the music is the point. How the tune got stuck is immaterial, later on.
All for now..
Gordon