I see this all the time and it's such a ridiculous mistake.
If there's no blood warden, and only 2 survivors in the match, and your teammate is about to be hooked for the first time DONT LEAVE!
You don't have to try and save them, but when it's only 2 survivors left, your teammate can attempt to unhook themselves. They might get the 4% or they might have Deliverance. But if you walk out before they get to attempt, they die instantly.
That's right, many of you have killed your teammates for absolutely no reason whatsoever. You weren't forced out. The killer couldn't pull you back in. Nothing. You just left and literally killed your own teammate.
Just stop. Wait as long as you can safely. Give your teammate those few precious seconds to make an attempt for freedom. Don't be a nerd and kill them off prematurely.