LilyPond is great, but the writing process for a lot of music involves a lot of playback, so integration with a half-decent playback engine is really useful. On top of that, you can do almost everything in Dorico and Sibelius with keyboard shortcuts, so they are very power-user-friendly (which is what I like about LaTeX).

Plus, as professional software used by people along (mostly not very much) money with it, productivity is key. Lilypond loses badly here.

I can enter 200 or 300 bars in Dorico in the time I could do 20 in Lilypond - and that’s at the rate I could manage when I was using lilypond regularly.

I also think the output is nicer, which also matters here.

Lilypond is for music typesetting (they call it "engraving").

Finale, Sibelius, Dorico, MuseScore are primarily for composing (though they have each made their own strides on the engraving front too).

Lilypond makes gorgeous music. However, getting things besides music to look good is painful at best and sometimes impossible. I spent hours trying to figure out how to get a good looking lead sheet setup (music, chord name, lyrics). Especially font sizes and spacing. Ugh. Good luck getting an annotation (such as "intro" or "chorus") anywhere less than about 2em from the top of the staff...

I think they've changed things in the five years since then, so I think I'd have to do it all over again.

I do "professional" engraving as a side gig, mostly turning scratch people's make on lined paper into actual sheet music, and I exclusively use lilypond