Lol unless they all were already in the same fireteam, & he was on a different part of the map, when they say they need back-up he comes across the map, in on a sparrow. A 3 person fire team can stretch across a entire map. It would also be boring to see the dullness of them unnessarily bringing him in like that when he didn't need to even be brought in if he was already in The Fireteam to begin with. It was also to show off gear/the sparrow not the working mechanics of the game. PS: I know the spot the entire trailer takes place, I call it the war zone - it's just a little before the array. as it had a bunch of fallen & hive fighting as well as a hidden Level "??" near-by on the side of a cliff. I looted their a lot. Infact if you didn't jump off your sparrow you could drive your sparrow their, through the buildings lol.