It's funny, I've been pondering that same question, Liam. It certainly is "folk process". But is it right? (and it happens to the tune equally)
I've recently inherited the job of co-editing a newsletter songpage, and we started out with this goal of publishing the song as the author wrote it. [Of course!] But as we go along, I am discovering over and over that 1. I have not heard the original version of the song; 2.the song and tune have changed substantially over time, and 3. I like the changed version better.
I'm pretty sure it IS human nature to like the version of the song one hears first. Most of the time, anyway.
I guess I'd like us to publish both versions, the processed and unprocessed, but space is a concern, and then sometimes the song gets processed in several different ways.
Take the trad song "Going to the West" (can be found here with a forum search). Peggy Seeger popularized it, and I believe she is the person who changed the person leaving from male to female. ("You say you will not go with me/you turn your face away....)The song sat in someone's archives until for more than 100 years, and then surfaced. It's a tricky tune, too. It alternates between 2/4 and 3/4, and I imagine that, by now, someone has evened that out. Early on, grace notes were added and the first line pickup was made more accessable. Did that improve it? Good question.
I thank Bruce Olsen for making the original available to me, and he performs an invaluable service by collecting these.
I think it's kind of like heirloom seeds. We don't want to lose the original stock, but a lot of times the hybrids are much tastier. (And sometimes they are just pretty and bland and easier to market).

But there's another part of singing a song, and that is making it speak. The songs that I sing best are the ones that move me, and that is because they tell something that matters to me personally. So as I sing them, I put them into my language, sometimes without even realizing it.

A long time back, I heard Michael Cooney differentiate between 'performers' and 'storytellers' -- performers being more interested in the dynamics of the song and its presentation, and 'storytellers' being more interested in telling the story. He said he was one of the latter, as am I. Telling it right gets me that silence at the end, and a sigh maybe, before people applaud, or even move. Performers get ovations, cheers.

And finally, tunes and words change based on our ability. Should you not sing a song because it is too hard? Try it anyway? Should you simplify it? Do what you can remember?
I'd say, all of the above... depending on your audience.
Blessings,
Barbara