PLUS, in the PS system, when the back seater talks, only his microphone is active. This is an important aspect because the intercom voice activated feature will probably be overwhelmed by the noise. With a PTT intercom, you push a button to talk to the other cockpit like you do the tower. Just a different button is all. There are also custom grips available with more buttons than my kid's Nintendo.
Nothing is more important to any phase of aviation today than communications.
If you are boring holes in the sky, chances are that you are not alone. Using the radio and telling someone that you're there can save your life. It could have saved a few in recent months. Talking to your formation mates and crew members is vital. By the same token, good crew communications inside the airplane is also vital.