"Certainly you should practice and try to attain the best performance you can, but having the words in front of you in case of a 'senior moment' can only be of benefit to the audience and shouldn't detract from the delivery."

Really fed up with this "senior moment" crap. But of course in this part of the above ".... having the words in front of you in case of a 'senior moment' can only be of benefit to the audience and shouldn't detract from the delivery." - The SHOULDN'T being the operative word. The reality is however it does detract and detract massively from the delivery compared to someone who has:

A - Learned the song
B - Sings it in key
C - Has worked out the phrasing of the song to deliver it in accordance with their interpretation of it

None of that can be done whilst hesitatingly reading the words while trying to sing them.

If you are seriously trying to equate someone singing a folk song to a group of people singing in a choir, or playing in an orchestra then I am sorry you are knowingly comparing apples to oranges as the latter two disciplines are NOT solo performances but multi-part collaborative pieces where those involved are singing and playing under direction that requires the highest discipline and perfect timing. The Score you see in their hands let's those holding them know what the others are doing and tells them when they should come in, something you do not need if you are performing on your own.

By the way someone sat there in public attempting to play and sing something that they haven't bothered to learn in a halting and hesitant manner, intermittently apologising while they stop to scroll their tablet - would not under any circumstance count as any sort of performance.