Because the dev team had some issue with the digital version they were working on breaking when the player would fast travel between the city and batcave. As far as I know, it was just that the game would crash and it required a hard reset (the PS3 version had the same problem the first week it was out but happened more often), they would have fixed it, but they got bumped to another project super quickly so the digital version wasn't released.
If you like 2D sidescrolling action games you will probably like Blackgate. It's underrated, imo. You should give the demo a shot.