I suppose you don't live in a dense city with a lot of indoors and underground infrastructure. In some places you easily spend half a mile indoors between underground train platforms or to the exit on the surface, or in walkways inside and in between buildings where there's no reliable signal. Other times it's simply because part of the commute goes through tunnels or the entire trip is underground. This really breaks a lot of useful tools, for example location based alerts or simply using navigation to get to the correct exit of a station (office, mall, etc.) which if you get it wrong can mean an extra mile of walking.