Yeah but triangulation is difficult and time-consuming, plus far from exact. It also requires knowing where somebody is at, else you'll be triangulating Baltimore when the suspect is over in Philly. In contrast GPS is like a big sign that says, "Here he is" as it moves across the cop's map. It's precise, instant, and easy
Well, to be clear, triangulation is easy if you are the cell company or software running on the device. Google maps has (and still does) used triangulation to get pretty accurate location for years - before GPS was as common or when GPS signals are unavaliable. That still requires hacking either sprint's network or the device itself, but it's just good to be clear that not having GPS on a device doesn't save us much.