@wetb4igetinthewater mentioned a diver should not be afraid of not having a reg in their mouth for 5 seconds or reconsider diving as a hobby, I suggested 30. It is not about the time it takes to execute a simple procedure, but how long one knows they can function without air, if and when an air share, or anything else, goes south.
I don't really miss buddy breathing because I've seen too many divers that just can't wait for the next breath, even though it's only a few seconds away. Some have the discipline to wait, others panic. It all depends on how long they can think clearly with a reg out of their mouth. It's a skill that is no longer considered important.
Diving is not just about how easily skills can be done, and the pretty fishes, but how well one can think and act when stressed, and not having air immediately available is stressed.
Bob