Over the last forty years, a large % of my music income has been from sight reading in professional pit & stage shows, arranging and work for music engraving/copying companies.
I haven't used pen and manuscript for years (Feather Quill, ink and gaslight even longer), It has mostly been using Sibelius or Finale (and now Dorico) on Computer.
Reading (and theory) for me, has been worth it's weight in money. So yes, definitely important from my point of view. 👍