There are so many reasons communication is essential. I can't tell you how many times I've had micless teammates go down and insta eliminated before I've even had a chance to figure out where they are. If they find weapons or meds they can't carry, I can't know it's on the ground if they can't tell me. There's no potential to plan a place to lay down a base. You either, as the guy with the mic, need to decide for the people without them or just start building when they randomly decide on the right time. There's no planning involved in those situations. Say you know the micless teammate is being attacked. If you don't have an idea of how many guys he's taking on (in Squads), you're running in blind. One Squads game my squad dropped at Snobby Shores. My teammate dropped second house on the left, me middle. He supposedly finished looting his house and moved over to the far left one. I saw him start to take damage so I booked it over to his house. Built a ramp up over to his wall and jumped over expecting one guy since I only heard one gun being fired. If the guy had a mic he could've warned me the entire squad was there and I was met by tac shotgun blasts, two ARs, and a RPG blast to wipe me out of the game in a matter of seconds.
Sure, if there's enemies away at distance, eventually you're gonna see them and a mic is not needed. And I've won a few squads games before voice chat was implemented in the game. But as a whole it pathologically annoys me if I get a full squad of people with no mics. There's no excuse for it. You can go to Marshall's or Ross and get a pair of headphones with a mic on it for 5 dollars.