Based on my experience as a former 1.25 - 1.5 player, I am never, ever matching against people who are below me. My best guess is that these people are sheltered. We used to play against these people in past games. With the holidays, COD was on sale for like $30 multiple times, yet I saw zero Xmas noobs. I'm pretty sure none of us did.
Youtubers have reverse boosted and gotten into these lobbies, so we know they exist. There are lobbies with players who can't even move and shoot. Obviously COD still sells great, so noobs are there. We just never, ever see them. If noobs aren't even playing against someone like me, you know they are in trash lobbies, because I'm nothing special. I've probably barely got a 1.25 in TDM in the past few games.
I'm put into tougher lobbies, because I am decent enough to "hang" and only be a .8. They've turned me into the new noob. I'm with you on camping, I won't do it either which is why my stats suck, but if I want to sit and hold angles all day, I'll play Rainbow Six.
I'm sure some noobs are "graduating" into my bracket, but I don't see very many of them. They have to be in their sheltered lobbies. The system isn't really SBMM but a skill tier. I'm clearly in the positive k/d up to at least 2-3 bracket, which is why I get thrashed. Some noob out there is now positive and loving the game and not knowing why. It is because they are sheltered from players even like me.