Wasn't there mention of a new API or SDK made available in the iOS 9 keynote? I swear it was called ReplayKit or something to that effect. Which could allow developers to add recording and such. I believe Procreate on the iPad Pro (maybe all versions) uses this as it records all your strokes from beginning to end of what you draw, paint or whatever. Allowing you to watch it as a "replay" and export the video.
Game developers could add similar, but unless they go through the effort to, I believe your only option is what's been mentioned and to plug in your device and use QuickTime on a Mac.
There was indeed, as I mentioned above its not actually difficult and really doesn't require much effort at all to implement.
The only issue with it is that it does eat into your available processing power. That alone can be enough to exclude it from some games as the more technically demanding the game is, the less you can afford to spare any of that available power.
Then you also have to consider older devices. The older the device, the less powerful it is, to the point where some devices just can't cope with the recording enabled. Even something like an iPhone 5 can really struggle to record game footage with even a moderately demanding game.
And by demanding I'm not really referring to how visually pleasing a game is. I mean the game logic that's happening behind the scenes. You can have a visually basic game that requires a massive amount of calculations going on in the background. Likewise you could have a visually beautiful game that's actually quite simple as far as the logic is concerned. So there are many aspects to consider.
So for some games it's not included, not because the developers don't want to, or can't be bothered implementing it. They just don't want the overall experience to be adversely affected by using it.
You could limit the recording to be available only on newer devices but again developers sometimes just don't want to put up with the complaining from owners of older devices that they are missing out on features. And if there's one thing people are good at its complaining, just read through almost any games reviews, the complaints often far outweigh the positives. Even if there's something out of a developers control, say Game Center having an outage. People will flood the reviews with complaints of the game being broken, when in reality it has nothing to do with the game or developer. I'm not being rough on us as consumers, it's pretty much the norm for any product that people who write comments are far more likely to do so for a negative thing than for a positive.
So when everything is weighed up its often just a reasonably sensible, as bad as it sounds, decision to leave gameplay recording out of a game for the overall satisfaction of the consumer.
I think by the time the iPhone 7 and even more so the 7s are available, that gameplay recording will become far more common. Simply because by that point a large percentage of devices in use are going to be iPhone 6 or newer and so will have the available overhead to cope with recording.
All that said, as far as an apps ability to record the screen of the device regardless of what other app or game is in use. I don't see that happening for a long time, if at all. I think Apple are likely to continue to limit the recording on an individual app by app basis. If for nothing else than security concerns, I don't think they're too keen on giving an app the ability to record potentially secure and private information.
They allow the recording via QuickTime on a Mac because if you are doing it there you are in complete control of what is and isn't recorded and when and of course because we, developers, need an easy way to record footage for the AppStore.
But you're also significantly less likely to forget that you've started a recording while you send a saucy text message to the wife doing the recording on your Mac than if you had enabled some app on your device to do the recording in the background
Dear god I can waffle on when my medication kicks in