There have also been delays on Mac games released on specific stores - they might hit the Mac App Store before Steam for example. Steam and SteamPlay can cause business headaches in the case of ports, and that also takes time to sort out. On top of that, if it's on the App Store, it'll need Apple's Game Center adding, and other multiplayer/achievement code removing or suppressing.
Maybe it's no surprise, then, that Aspyr Media, one of the biggest Mac games companies - responsible for the BioShock Infinite port, among others - employs more staff in QA, sales and marketing than it does in engineering duties.
Going native
Life gets a lot easier for developers if there's no porting required in the first place, of course. Engine changes to allow easy cross-platform development are already happening, with smaller, nimbler games seeing the benefits currently. Unity supports everything going, meaning that games such as Gone Home and the alpha for Sir, You Are Being Hunted arrived on Mac at the same time as everything else - including Linux.
The iPhone helped Apple overall in cross-platform support, getting engine developers interested in making it easy for game devs to put their products on Apple-powered devices (for example, the iPhone's iOS is based on OS X).
SteamOS could be the next platform that helps Mac owners. Linux and OS X are far from identical as operating systems, but are close enough that some games run on both in a single binary. Basically, if developers put in the effort to make their games work on Linux, it's not a big step to Mac, and Valve's attempt to get as many games as possible to go cross-platform could be the final step that puts the Mac on pretty much level pegging with Windows for games support in the future.
You might ask, very fairly, why it would take Valve throwing its weight around to make this happen when Apple is pretty hefty itself. The thing is, Apple just never cared about gaming before it became a key selling point in the iPhone, and even now is much better at saying it's doing great things for gamers than actually doing them.
While games companies have been making the moves to get their products on Macs, Apple itself has been slow to help. The problem is partly technical, but partly it's just a failure to engage with what's expected of PC games.
Steam's presence on Mac brings all the usual goodies, like cloud saves, social features and achievements. Not long after Steam arrived, Apple launched its own Mac App Store, and the hope was that it would be another good platform to discover and buy games, especially for people who wouldn't have heard of Steam. To a degree it succeeded, but only for people who aren't used to the kind of features offered by Steam. There's nothing like the ubiquity of Steam Cloud for online saves, and the social features are tied into Apple's Game Center service, which is barely used.
Most irritating of all is the requirement that all Mac App Store games be sandboxed, meaning that developers can't include any ways to tie games into your Steam account so you can see your friends for multiplayer there. The Mac App Store is convenient, but as a gaming platform, it just doesn't compare.
Dem graphics
Then there's the state of graphics support in OS X. It hasn't been the best. Because all of its hardware is so slimline, Apple is loathe to use very large, hot GPUs, so it tends to go for mobile cards, even in desktops. That's still okay - there's great gaming to be had in a Nvidia 750M or Iris Pro - but the drivers often seem to be inferior to their Windows counterparts, and can vary from card to card.
