Why Would An Artist Re-Record Portions Of Her/His Own Music?

I want to briefly explore the different means, causes and reasons why music is re-recorded. As always, I welcome readers' input. So far, I have been able to identify more than one dozen reasons to re-record music. This might be tantamount to saying, "more than one dozen categories of re-recorded music." I'm not ready to shout out, "Here is the definitive list of how, why, what, where and when music is re-recorded." For now, this is just a beginning and an interesting pursuit into an area of creativity and originality.