You might have noticed that on with Windows 8 Installing a Video Device Driver would no longer require a Windows Restart. However installing a Wireless Driver on Windows 8 would still require a Windows restart. That’s because Windows 8 Architecture has really evolved much further toward Micro Kernel Architecture. The original Windows NT 3.5 was supposed to deliver a Micro Kernel Design. The Issue is that an OS with a Micro Kernel achieves better stability; historically though Monolithic Kernels have been able to achieve better performance. Windows has decided to sacrifice little bit of performance loss in favor of stability because Nowadays our Processing power mostly sits idle and we have much more memory on our Computers.
You can actually verify this because in Windows 8 if your video driver Crashes your screen goes black for a second but Windows does not crash just because the Video Driver or Graphic Card was buggy. Back in Windows XP, Windows Vista and Windows 7 days, Windows Kernel was much more monolithic. Windows XP crashed when you had any faulty drivers. But the interesting thing is that Microsoft has been focusing much more on stability these days. Windows Vista put in PatchGuard and started requiring all code running in Kernel space to be signed. Windows 7 Introduced User Mode Driver Framework in order to move up a lot of non-performance critical device drivers up the stack to the user mode of the operating system. Windows 8 has taken this further by introducing Micro-Kernel Architecture for critical Drivers and Filter Drivers and Virtual Device Drivers. This means that Windows 8 and Windows 8.1 are far more tolerant of Device Driver malfunction.