Q: just got a depressing insight into the music industry: apparently demos for songs get passed around and artists just pick them up and go, "oh, i'll sing this one." so like there's artists singing songs that they haven't written themselves? and this is fairly common?
A: sure, that's always been fairly common. it's like when you go see a movie, most of the time the actors did not write their own dialogue. however, i'd say it's probably more common for a singer to have written the song they're singing than for an actor to have written the part they are acting. but both situations exist for both, and there might be advantages and disadvantages for both