I guess with me I am recording to evaluate live performance.....so I want all my vocals single take to see if they are ready for live performance. I record vocals, backing tracks, and live instruments and then evaluate. It gives you a measure on mixing balance and performance. For me I seldom get thru a vocal completely flawless but totally acceptable. My fiance who has a fantastic voice is pretty much flawless.....drives me crazy. So none of this applies to why we comp...for me it just gives me some insurance that I have enough to work with. When I recorded my band for a demo I wanted it to be completely live so it was a fair representation of us live. Because we didn't do retakes just set up and played thru I had a few I had to toss because of issues I couldn't do anything with.