Apple's approach changed drastically over the years. Back in the 90s they were discouraging people from making apps that expected a screen size larger than 512

Apple's approach changed drastically over the years. Back in the 90s they were discouraging people from making apps that expected a screen size larger than 512x342 and color, because a lot of the installed base still had the equivalent of a mac plus. Your app was supposed to start with the basic functionality and ask the system if it supported more using the Gestalt manager. Then, finally, Open Transport made lots of machines obsolete and eventually 68k was gone altogether. Newer apps could assume 256 colors and at least 640x480. When they released Carbon, they were putting the handwriting on the wall for old apps. You will be left behind. Mac OS X frequently obsoleted old apps. Newer machines couldn't run your app, newer OS had different quirks and incompatibilities. New apps frequently obsoleted older machines and systems, just because. XCode made it somewhat less easy to code to an older standard, and if you did, it might not work in the newest system. Apple also had their writers chasing the latest and greatest look. Finished your glassy and lickable interface? iTunes is now brushed metal, you look so 2003. Got your icons' perspective looking like you're staring at the desktop? They're flat now, get with 2007. I think mac users have been happy so long as the actual machines last about 8-10 years before becoming obsolete, which they generally do. Phone users can make do with 4-6. But if you want to take an old app and run it, good luck. Apps are no longer finished products, ever. They adapt to the platform or die. * dates are approximate