Virtual theatre is by no means the same as attending a show in person with an audience all around you (hopefully), but there are several things you can do on screen that you can't do on stage. Here are a few of them:
1. Close ups -- The nature of having a camera on you at all times gives the audience a much closer view of the actor's face and body than they might get in a theatre. This can be both intimidating to the actor as well as offer an added feature to their performance that they couldn't give to an audience sitting several feet (or more) away from them; expressions don't need to be so exaggerated to get an emotion across, and whispers can be just that. This realistic touch brings the audience into the scene, and can present the action (through the use of multiple cameras) from any angle imaginable.
2. Seeing the unseen -- When a character opens a newspaper on stage, say, or sees something outside "the fourth wall" in a traditional playhouse, the audience suspends disbelief and imagines it in their head. That's enjoyable for some, but in virtual theatre, thanks to cameras being able to go anywhere, now the audience can get a look at it too, through the character's eyes. The added dimension afforded by virtual theatre can make the play like a film and invite in elements we can't get so easily on stage.
3. Special effects -- Perhaps one of the biggest boons of virtual theatre is that a director can use visual and audio effects that can't be done without a mega budget on stage. One can alternate backgrounds on a green screen, depending on the scene's location, they can have a scene take place in a thunderstorm where it looks like the actors are getting soaked, the audience can be shown a distorted view of something seen through the character's eyes, or even include montages (like flashbacks) that could be shown in black-and-white or sepia-tone lenses. (I'm still waiting for someone to do a virtual version of the musical City of Angels in that noir color scheme.)
4. Live on the scene -- I've worked with some amazing scenic designers who can create whatever the director asks, and make it look like almost the real thing. But now that we have virtual theatre, you can literally perform in the actual space your show requires. How cool would it be to see the legal drama The Last Days of Judas Iscariot in an actual courtroom? Or the highly-disturbing (and therefore amazing) Hand to God in a church? (Good luck with that!) Your virtual theatre company can be a traveling troupe of players who perform the piece in the room where it happens.
5. Expanding your audience -- Take my word for it, with streaming technology now a real thing, theatres will begin broadcasting their shows virtually, even if they're on stage before an audience, so they can be seen anywhere in the world. Thanks to virtual technology, if your significant other is on a business trip, or your grandmother can't make it to your show, now they can,.