What if they are selling well even with this behaviour?
During the Xbox 360 dominance something similar happened.
Games can skip a platform and do well, I won't deny that. At the same time, a game can skip a platform and do awful. Remember, no one is buying a console for an indie so if they decide to skip a platform, they need to make that the chosen platforms earn as much.
Also, the XB360 era was a different time. MS had Indie developers in a neck hold to publish their games through the XBLA. This generation is different, Sony isn't holding anyone by the neck. Some developers have created some kind of self allegiance to Sony while casting MS as some monster.
Armello and AAC come to mind.