After it was removed entirely
Amdist the launch of Titanfall's new DLC maps, there's a new matchmaking update afoot for the PC and Xbox One versions. Evidently "less than 1%" of players were using the Capture the Flag gametype on PC, so Respawn took it out entirely -- until late last week, when fan demand brought it back.
Since the game is online-only, that basically meant that there was no way to play CTF outside of private matches or the Variety list, and it was effectively deleted from the main way to play the game. As a response, the mode was re-added and better global matchmaking options are planned -- which sure seems a hell of a lot better than removing a giant portion of the already paltry game modes.
Maybe it's just me, but it's a pretty big shame that such a hyped game can't even find a steady stream of players for such a big gametype. There are still thousands of people active on Call of Duty games as old as the first Black Ops, which often adds playlists before taking them away.
CTF and Matchmaking update [Titanfall]