Just to be clear, this isn't about requiring anyone to do anything but as Madda says, and I find the same thing as well, that when people start talking and checking each other, the bad guys get cleaned up pretty quick.
That would make this a "good thing" to promote, not require. Even if you don't have a mic, you can benefit from the information that is flowing around.
The delay is a bit that we don't often figure on, because when you are just playing alone, you don't notice it. Like Wraithe, my son often plays next to me and we have seen delays of up to 3-4 seconds on messages. That makes the useful chatter even more valuable since presumably all friendly players would have a better idea of bogies in the environment and could be on guard.
