I also think it is sort of an extension of the rationale for playing covers, often covers are selected and learned out of an admiration and appreciation for the talents of the original artists it also follows that original material comes out of a want to take something that has inspired you and take it further or add new facets to it or just generally make more of a particular sound or genre you authentically enjoy..
I also believe there is a huge difference between playing a cover by simply parroting what the original artist did or playing a cover by re-interpreting the original artist's work in a way that is genuinely you, sometimes interpreting covers is a great stepping stone to getting to a new plateau of writing your own material.
+1 on this, I feel exactly the same way about covers. I've only done a couple, and there are some others that I'd like to do in the near future. Honestly, doing covers has helped me in multiple ways ranging from learning better tracking and mixing techniques in my DAW (Ardour) to learning how to write more coherent song structures.
I agree that there's a huge difference in just emulating note-for-note and tick-for-tack another musician's original material, but for me personally sometimes it's nice to be able to focus on DAW techniques (and even some musicianship!) when a song is already laid out for you (in terms of structure, lyrics, instrumentation, etc. etc.). When I first started pretending to be an audio engineer
I remember feeling a bit overwhelmed and scatterbrained trying to learn how to hone my workflow and DAW skills at the same time as I was trying to write music that wasn't totally confusing and crappy.
I hope to (one day...) be able to take a cover and be confident enough to make it my own and interpret it my own way. I think that's a sign of maturing musicianship there (Nirvana's "Man Who Sold The World", Joe Cocker's "With a Little Help From My Friends", and the list goes on and on and on...).
Again thanks everyone for sharing your thoughts, it's been great reading for me!