The App Store isn't what it used to be back in 2012, so it's not unexpected to see some games changing their structures with the times. Now we can add Rage of Bahamut to that list with the recent announcement that the game is severely cutting back on the number of events it holds.
I've been playing Rage of Bahamut on and off ever since I wrote that review three years ago, and I have to say it's a real shame to find out that every kind of event except Onslaught is being put on "permanent hiatus." As someone who prefers PvE (player-versus-environment) over PvP (player-versus-player), I always enjoyed logging in to find a new series of special quests to complete and new rare cards to collect. No reason for the removal of events has been given, but if I were to venture a guess I'd think it has something to do with having to produce so much content every time a new one comes around. I mean if you think about it, each event adds several new cards (that's four new pieces of artwork per card at minimum), there are special story animations, we usually get some weird special mechanics to deal with for event quests, and so on. That's an awful lot of work to put in to bi-weekly/monthly content.
I've reached out to DeNA to see if they'd be willing to explain the decision to remove all but one type of event from Rage of Bahamut in a bit more detail, but with the Independence Day holiday kicking off there wasn't anyone available to comment. I'll be trying again next week and will update accordingly if I can.