Because upscaling algorithms have gotten incredibly good, and this film makes specific use of HDR (High Dynamic Range).

: Action sequences feature precise directionality, tracking bullets and drone movements across the soundstage. Collector’s Extras

The 4K presentation is a notable step up from the previous 1080p Blu-ray, even if it isn't a "night-and-day" transformation for everyone. Refined Detail

: The 5.1 presentation offers punchy low-end for robotic movements and explosions, with dynamic audio cues that move seamlessly around the room during action sequences.

The highlight, quite literally, is the character of Rick Mattox (played by Jackie Earle Haley) and the tactical HUD (Heads Up Display) interfaces. The vibrant reds and cyans of the digital targeting systems pop with an intensity that standard definition simply cannot replicate. It makes the inside of Alex Murphy’s head feel genuinely high-tech rather than just a visual effect.