As dramatists, we depend on actors. Acting underlies all theatrical work. It is good for us to do scenery and lighting, but it is even better to do acting and directing. By doing this work, we can see how a script comes to life, in sound and spectacle, on the stage. When we give scripts to dramaturgs, or even playwrights, who are not actors or directors, it is like giving sheet music to non-musicians.
Our plays, of course, are written for the general public. This public need not be stage literate. The spectators will bring their life experiences to the theatre, and these experiences will test everything they see and hear onstage. Playwrights have understood this since the theatre’s beginning.
And on the subject, something should be said in defense of Bernard Shaw and Eugene O’Neill. They are now criticized for writing way too many stage directions. But we should look the historical context in which they wrote.
The incomes of both Shaw and O’Neill came in part from the library editions of their plays. O’Neill was one of Random House’s best selling authors. By their full stage directions, these playwrights made their plays easily comprehensible to the general reading public.
Actors and directors are free to disregard the stage directions.