Sony introduced Share Play on the PS4 to allow multiplayer and co-op gaming over the internet without both gamers having to own the game. The catch was it left the option to include this feature open to game developers. Activision isn't playing along.
Share Play allows a person who owns the game to invite a friend also on PlayStation Plus to play too, over the network, without them owning the game. This works for one-hour periods before cutting out. But you can then just re-join and carry on.
The Call of Duty: Advanced Warfare and Call of Duty: Ghosts creators aren't allowing people to play their games without paying for them. Share Play has been disabled on both of the titles.
Eurogamer contacted Activision and was told that because Share Play is still a new feature its engineers haven't had the chance to test it properly.
The reply included this statement: "Our engineers didn't have access to it before it launched, so we haven't had a chance to evaluate it to see how it will impact the experience across all modes of play. Of course we wouldn't include a feature in our game without having the chance to test it. Once we've fully analysed its performance, we'll determine how to support it going forward."
So it would seem the Share Play feature wasn't disabled to sell more games, on the surface at least. Indeed this response would suggest gamers can expect Share Play to be added in the future.