But is being a musician a job? I think of how Paul Simon said in an interview that although most people his age are retired, that he can't just suddenly turn the songwriting side of him off just because he reached a certain age, its part of who he is and he'll be writing music until the day he dies.
Whether being a musician is a "job" or not is completely subjective - depending on the musician you ask. I guess some are perfectly happy to retire and live off the fruits of their labors ( or move to a whole other career) and some feel compelled to do it regardless. My dad is 71 and has no plans to retire because music is his job, his life, and his only hobby. He'd be bored to tears if he didn't have music.