Apple pays more attention to the details then anyone else. Sometimes the details they pay attention to are so small, you don’t notice them at all for a long time… but once you see what they’ve done, you can never unsee it, or accept anything less.
Here’s a great example from OS X Yosemite. Compare the two images above. The top is from OS X Yosemite, the bottom from Windows 7. Notice anything? One of these images has much better typography than the other. But can you tell why?