I use them to isolate my Favorites/System/Departments to what I'm listening to or where I'm located. I live in Illinois, travel to Indiana, Michigan, Wisconsin, and when I'm there, I can easily turn on or off a county to control what I'm listening to.
Indiana has it's own favorite list (81), each county is assigned a system 1, 2, 3 etc. (81.1/81.2/81.3), and on each system is the site(s) per the county I'm in (no quick key used). I can then break it down further to police (1), Fire (2) Etc. If I don't want to monitor Fire Departments for example I press (81.1.2 Enter) Off appears and I know I further isolated my listening.
I also can assign the State Police their own System number, to isolate my monitoring to highways. In that system, I program all the sites of counties I pass through (No quick key assigned) and they have their own System (21). If I'm traveling the Indiana Toll Road (Dist.21), I can simply press (81.21).
I don't use GPS, or import from the database, but do it myself. My scanner is set up my way, and isolated to what I would like to listen to in the specific area I'm in. This is just one example..