In my experience, LilyPond *is* capable of producing scores of the
highest caliber. However, I often spend so much time tweaking the
score to get it to look perfect that it really becomes a labor of
love. I think until LilyPond is able to achieve that perfect type of
score with minimal effort, employers at firms that produce music
scores will rely on software that is more intuitive and gives quicker
results - they have to pay someone for their time to notate this
stuff. Meanwhile, I am convinced LilyPond's output is capable of much
greater beauty than anything else out there... but I frankly don't
think it will ever touch a very large user base (compared to
you-know-who).
I am curious who out there is in a professional music-related position
that relies on Lilypond when Finale or Sibelius is also an option
provided by the employer. I'm one. Just curious who else.
For whatever it's worth.