There are two voices I hear here vis-a-vis Bach:
1. Art for art's sake -- the romantic idea
2. Art for money's sake -- the distinction of commercial vs commisioned being a fine semantic distinction.
Bach himself expressed a view however which does not fit in with either:
Anything done other than for the service of God is vanity
[I read this 30 years ago and google is not finding me a suitable quote -- sorry if its off the mark]