That’s completely different. One of my good friends is a bartender. But his passion is his music. He’s practicing with friends, performing in front of people, etc. It is a social event - not sitting at a computer all day.
For years I was a part time fitness instructor and runner. I loved hanging out with friends, being in front of people, meeting them at races and us training together. It’s completely different than being at a computer at home - after working all day on one.
You're missing the point. Your good friend has to work on his music outside of his paid profession. It's a hobby that is not financially viable for him as a career.
You expect someone who writes software for 8+ hours a day professionally to go home and do more of it for fun?
Those who are interested in doing that are free to do so, but most people have more than 1 interest or would like to be compensated for the additional hours they are effectively working in their profession.
Rereading I can't edit now, but I meant there are plenty of respectable musicians who are not like this as well as plenty of great talents that only perform professionally.
Not that one or the other is a less-respectable approach.
And plenty who are not, it takes all kinds.
It's a matter of taste and still all tastes may not be satisfied anyway :)