(Now before any comments are spoken on this, please don't flame me on this topic!!! I am simply asking.) I wanted to ask, what kind of games do not need to have a pause function? Or do all games, no matter how small or simple, need to have pause? I am asking because one of my games not mentioned in my sig is so simple, its pretty pointless to have a pause function. it's a small, casual game that you play until you run out of stuff to drop, and then you restart again.
I don't think the pause function is a requirement for all games, and it will depend on whether it makes sense for your game in terms of user experience and gameplay. Maybe when you beta test the game, you can have some people try out one version with a pause button and some without and see what they have to say about the presence/absence of that fuction?
An in-game pause function might not be needed for every game, but you really should add some sort of pausing to gracefully handle system interruptions - phone calls, alarms, notifications, music player, etc. Once you do that however, you might as well just add a proper in-game pause too.
The thing is it's not the game that matters, even a short game. If you can pause a game for more than a few seconds you can probably not get back in the 'zone'. Pause a driving game and when you come back you'll probably screw up the first corner if the break has been too long for you. Fast paced games like Canabalt are the same, fast puzzle games too. Where reaction is not an issue then I don't suppose it matters but otherwise I think pausing a game could be a problem. And if you are anything like me it's always the best games that last just that bit longer than the others and you have to pause. And it then goes wrong...
I have played plenty of games that don't require a pause; like Drop7, Smiles, Solitaire, Minesweeper, etc. It depends completely on the type of game. I think, generally, if a game has any time elements, has any reaction mechanics, or accelerometer use that could result in accidental input, you should put a pause in. At the end of the day, you'll discover if your game requires a pause screen or not while beta testing.
Turn based games don't need a pause button. I think they are perfect. I've just finished mine and am about to upload it to the app store. It's called Barbarians: the fall. Look out for it in a couple of weeks(months).
Having a 2 yr old that loves to grab things. I believe that ALL games should have pause function. That or a auto save/resume incase the battery dies or some "Little" one steals my device mid level.
The real problem, is what games shouldn't have mute when the iphone is in silent mode? There has been more than once or twice when my phone starts blasting random game music from an app I just bought during lectures =/