When I read American Beauty, I was amazed to see Alan Ball's use of 3 or 4 parentheticals per page. Since then, I've been using them, though not so many as Alan. If the entering injured character is about to say something, I might write
Otherwise, I'd write it as an action line. But I think every writer has his own style.
1. By the time Alan Ball wrote American Beauty (which I love btw), he was already fairly well established as a TV writer. Screenplays by established writers can get away with things that the rest of us may not be able to.
2. When we see screenplays of already produced movies, they are frequently produced after the fact, meaning that they don't necessarily reflect what the screenwriter originally wrote.
But yes, definitely we all have our own style and this is all just my opinion
As a spec writer, I may write in a parenthetical so as NOT to disrupt my FLOW but I would rarely LEAVE it as is if it's actual action. Eventually however, you tend to teach yourself to no longer write that way.
Having said that? I've seen many shooting scripts that contain lots of parentheticals but as we've discussed here many times... That's a shooting script. Unfortunately, most specs I read of people trying to break in tend to emulate shooting scripts because that's what most people attempting to become screenwriters can find online.
And of course... As we've discussed many times before... If you're shooting something yourself? Write it any way you want. Place as many or as little parentheticals as you need wherever you want them. In a spec though... Especially when it comes to marketing time? I think you'll get more mileage out of your spec if you keep parentheticals down to a complete MINIMUM.
For instance... I only use them when there are more than two characters speaking to each other. When it's NOT obvious, you might place a (to CHARACTER WHOMEVER) parenthetical below the character cue.
Or... If your character's speech fluctuates and it's IMPORTANT to the scene... i.e., (trailing) or (trailing off).
In other words? If WORKS in an action sentence/paragraph? Probably best to stick it there.