First off, there is a huge base of players that want nothing to do with crucible, but want to complete bounties, quests, etc. Most of these players could care less about the match, because they don't want to be there in the first place. They feel forced to be in the Crucible to get the gear they want, or to complete the bounties to advance their levels faster. Blame Bungie for making quests and bounties that require crucible, that brings players into crucible that only want the items from the bounties and quests, and only play crucible to get them. Blame Bungie for matchmaking that makes those players not care about trying or about ruining the game for those that are trying. When you know you have no chance, why even try? This is the new attitude created by matchmaking that puts average players and lower, against the best of the best. They don't want to be there, so they have no incentive to care about the other players on the team.
I mean you are not wrong, But the majority is actually crucible people not caring for a number of reasons. I see dudes with Crucible pinnacle weapons, who have garbage team skills. They just dont have any Etiquette , and its not because they dont want to be there. Lots of people back out, or fly solo just to better their stats. Or they join the game, and decide not to commit to it. Its a lot of reasons, not bungie's Quest and bounty system exclusively.