I believe all publishers would love to have all of their past games available for BC. But the process takes time, so it makes sense for most to want the focus to be on the games they believe have the most potential to bring in new purchases.
Activision in particular, I imagine is really for it now if they weren't before considering that BC being made available for COD: BO2 (5 year old game) made it grab enough new sales to propel it back into the NPD top 10.
And if you look at PC, the availability of old titles doesn't restrict the sales of new titles, and if it does it's a relatively negligible effect. And remasters are sold on PC just as they are on console. Not everyone that already owns an original copy of a game buys a remaster, but quite a few do just to get a nicer looking version of a game which sometimes comes with updates to the gameplay (new Age of Empires remaster is reworking unit pathing, for example). But again, that is no different from consoles.
I was thinking about COD: Ghosts getting a lot of requests for BC despite there being an XBO version available. And I think I might know part of the reason for it. Performance (stable FPS) is absolutely essential for COD due to how much it focuses on competitive multiplayer. In other words, performance consistency is far more important than graphical bling. COD: Ghosts exhibited a LOT of inconsistent performance on XBO, especially after the DLC packs (
http://www.eurogamer.net/articles/digitalfoundry-2014-performance-drops-on-cod-ghosts-patch ). It might be that there are fans of the game that want a BC version in hopes that it would offer more consistent framerates than the XBO version of the game.
Regards,
SB