There's a habit to have way fewer people 'stand in' for larger groups--like having a Squad or a Fire Team "stand in" for a Platoon or Company. Part of that is screenwriter laziness, a full-up Platoon is about 50 guys, and that's a lot of names and character identities. Part of that is cheapness--paying for 6-7 guys is cheaper than hiring a Platoon of Extras at Union Scale. Part of that is the persistent notion that the General Public can only 'follow' a certain number of characters through a story (despite the success of large ensemble cast programs). But, a significant portion is from just not groking how that works in real life. Jeremiah Johnson is one man against the wilderness. PFC Smith has 3 other people in his Fire Team, and there are two more Fire Teams in his Squad, which is one of three in the Platoon, one of 3-5 in the Company, and on and aon up the chain.