Luckly nobody wastes time trying to find them each game.
I wouldn't say that's true, at least on hard and even on suicidal and hoe when the maps first realease. I've joined plenty of games with one or two guys kiting a clot around looking for the collectibles. And everyone else just sits in spectate because they are too lazy to get the achievement themselves. People join and leave frustrated that they can't play. Its by no means common but I have seen it happen plenty of times.