Every OS you've ever booted on real x86 hardware — from DOS-era systems to modern Linux — passes through this exact real-mode-to-protected-mode transition, and forgetting the far jump after setting CR0.PE is a rite-of-passage bug that leaves the CPU executing stale real-mode instructions until it triple-faults. This is also the leverage point where early teaching kernels like xv6's x86 predecessors first became genuinely 32-bit.