Why is choking someone into unconscious normally an assumed death in movies? Don't they have a chance to regain consciousness?
In the real world? Yeah. Killing someone by choking takes a long time. It’s a legitimate way to kill someone, but not an efficient one, and the timeframe you see in most films is a fraction of what you’d need to kill someone. It is worth remembering, this can kill you. This is one of those times where “safe” does not mean “non-lethal,” just that it is not immediately lethal.
In films, choking is an ideal option. In a controlled environment, it’s (relatively) safe. You can get both actors in frame together. You’ve got a lot of options to set up the shots. Finally, it’s incredibly easy to fake. You get the actors into position, one of them, “chokes,” the other without putting any pressure on the windpipe or arteries, and play the scene out.
It’s probably worth remembering, (even if some actors forget this part), that acting is a cooperative exercise. Your job isn’t just to hit your marks, spit your lines, and (occasionally) devour any unattended scenery; you also need to facilitate your fellow actors’ performances. Stage fighting is an excellent example of this. It’s not about actual violence, but it is about working together to create the illusion. If anyone gets hurt in the process, that means you can’t just reset and do another take, so this is something that the production staff and performers really want to avoid.
There are a lot of staples in film and stage violence that do not translate to the real world. They survive because of a few factors: most people don’t know what they’re seeing is unrealistic, it facilitates opportunities for acting, and it is reasonably safe.
Choking is great on film, because it gives both actors plenty of time to do whatever the script calls for. So long as no one is actually having trouble breathing, they can do this all day until the shot comes out right. Characters die from this because the power of plot compels them to, not because of any physiological considerations. Audiences believe it kills characters because, “well, I’ve got to breathe, right?” Without ever questioning how long they can actually go without oxygen. The idea that effective chokes are about cutting off the flow of blood to the brain never occurs to them.
If an actor does screw up, and accidentally starts choking their coworker, you have a lot of time to rectify that. This isn’t true for a lot of stunt fighting, where if someone screws up, someone’s going to take a hit, and all that’s left is apologies, or in some tragic cases, obituaries.
Choking, depending on where you put your pressure can also include some insane stuff you probably wouldn’t think is safe. An example would be the one handed choke that lifts the victim off the ground. You can do this a couple ways, the easiest (without rigging) is to push them up a wall, keeping your thumb and index finger under their jaw (against the bone), you’re actually lifting their head, their throat is completely safe, the airway remains clear, they can breathe, but it looks like you’re going full Darth Vader on them. Even for someone standing right there, it can be difficult to realize the victim is completely unharmed.
Beyond this, front facing chokes, like you’ll usually see in films, are very difficult to use in a real situation. As I mentioned above, they don’t really provide good access to the points you’d be trying to compress, but, they’re also difficult to complete because the victim has a lot of options. There’s a lot of counters to these, that range from simply pulling the hand free, to breaking their arm at the elbow. Wrapping an arm around the attacker’s and dragging it out of position will stop the choke, and tie up their arm.
So, no, this is something that’s used because it looks good on film, not because it has any grounding in reality.