I very seldom use my iPhone’s Spotlight interface for anything now that I can just use Siri to command almost anything I need. Nevertheless, the former still comes in handy when you want to find an app or perform basic math without using your voice.
Niche uses aside, Apple doesn’t provide any way of customizing the Spotlight user interface on a stock device, but jailbreakers can now take advantage of a newly released jailbreak tweak dubbed Spotlightizer by iOS developer 1di4r to bypass this seemingly unnecessary restriction.