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.

Sorry if my text can be misinterpreted so easily.