There's a big debate over these... some people say leave 'em out, some say put 'em in, some say actors and directors ignore them, some say actors and directors need them... etc.
In my world, the editor at Brooklyn Publishers says the more the merrier. Since a lot of their customers are first time directors, or people new to it - and many schools use student directors as well, he says they like to have a lot of direction, and even ask for plays that have a lot of author's notes and/or stage directions.
I've done some "directing from the page," and if someone wants to use that, fine, if they don't, fine, but at least it's there, and also I notice in this world at least, most directors want to do it the way the writer wrote it.
I wrote a play called "High School Spoofical" which is also the name of an Australian musical. Who knew? Both are parodies of "High School Musical," my version more or less is about a class that's putting on the play HSM but how things in the school parallel the plot of the show. (insert spooky music here).
Editor said "you have some great dialogue but right now it's just people standing around talking, and it needs action." Kids in high school like to move around, and again, a director might need some help. So for this one I went all out, and I put in a whole undercurrent of directions and actions that augment the dialogue but that no one would infer from reading the lines. I had a lot of tossing basketballs and throwing paper and just doing things...
Turns out this play's been put on relatively often, which makes sense because some folks are all about High School Musical, And it's fun play. I saw it once in Ashland, TN, and the director there used every last one of my extra directions. It really added a lot of the show, and gave people something to do besides talk. As a writer, I got a chance to see that "it worked!"
And... who hasn't seen a play where people come up to the front and talk, and talk, and... talk. and talk.
I like to compare this to music. If you see a piece by Mozart, you see a lot of "stage directions," it tells you how fast, how loud, staccato, legato, accented, etc. 222 years later you know exactly what Wolfy wanted you to do, and the best musicians are the ones who interpret Mozart so you hear Mozart. I believe with any piece of music as well as a stage direction, there are 1000 possible ways to interpret it "correctly."
Ragtime music often has nothing. Just the notes. It's a challenge... or an opportunity... then because you get to do what you want. Come to think, most people do anyway, but I try more now to incorporate dynamics into the rags when they're there. I had that challenge directing Helen, by Euripides... the firs 20 or so minutes in particular is a lot of Helen having monologues, so you get to find your own directions and make it interesting.
So upshot is, I'm trying to use a lot of notes and directions because that's what my audience wants. If the editor says "leave 'em out" I'll leave 'em out.
Interesting too, I like to listen to YouTube music where they have the score of the piece and you can see if they actually follow the directions.
You can, of course, find High School Spoofical at www.brookpub.com