A Boy named "Sue"

I wonder why a male singer would cover a song which has a female protagonist in first person, and vice versa. In some cases they adjust the lyrics to take care of the gender references – like changing “I’m your lady” to “you’re my lady” (Power of love, not sure which one is the original) etc.

Two brilliant covers I heard recently that doesn't take the pain (well, it’s not possible in these cases) to do a "gender flip":

Rosanne Cash – Long black veil (a live version here)

The White stripes– Jolene (Jack White sings Jolene Jolene.. pls don’t take my man, heh! Heard it on Sound Opinions)