I think they're making better strides than PC. Even if you buy a PC with a 4K screen, programs crash constantly and many of the buttons for PC look blurry because they are scaled up from their lower res version. They came up with a little patch for windows 8 to work with 4k screens, but it's just a patch not a ground up implementation.
Apple's OS as far back as the original Macs were designed from the get-go to scale with screen resolution. One of the reasons the Mac was so popular with publishing companies in the 1980s was because it automatically scaled the UI depending on your monitor size. The Mac would ask the monitor what it's size was, then calculate PPI based on the display resolution, and scale the UI the correct amount. This meant a 10 point font was always the same physical size on a Mac screen, regardless of your monitor size or screen resolution. The OS would scale everything automatically.
Windows took a different approach - optimizing output based on pixels. This meant the physical size of a 10 point font differed depending on your screen size and resolution. But it meant that for a given screen size and resolution, the output was sharper than using Apple's approach. You can see this for yourself if you ever hook up a Mac and PC to identical monitors side-by-side. The PC has sharper fonts and icons. In a way, the Macs
needed "retina" displays more than PCs.
Neither solution is "right". Which is better depended on the display technology available at the time. With low- and medium-PPI displays, the Windows approach was better. With high-PPI displays, Apple's approach is better. Advances in display and GPU technology have made Apple's solution better today. It does not mean it was
always the better solution.
Ironically, the situation is completely reversed in mobile devices. For some inexplicable reason, Apple abandoned the PPI-scaling approach they used on MacOS and OS X. They based iOS on a fixed screen size and resolution. That's why iPhones had to double the resolution (it was the only way to scale up the UI), and the UI on the iPad Mini looks a little too small (it's the same resolution as a regular iPad, but has a smaller screen). OTOH, Android has an internal PPI setting which you can change to automatically scale the UI depending on the screen size and resolution so the icons always remain the same physical size. If you hack your phone, you can even change this setting manually - give your parents extra-large icons and text for their aging eyes.