Originally Posted by wphamilton

1) for GPS navigation
2) if you're playing with strava segments, or timing intervals
3) if your GPS reception is spotty and needs to be out in the open
4) you want hands free phone operation
5) the phone there isn't flopping around in your cargo pants or getting sweaty in your jersey pocket
6) other applications you may wish to have.

Originally Posted by prathmann

Having a map display in a visible spot seems useful for a variety of bicycling activities. Sure it's not needed when close to home in a familiar area, but for longer rides it's handy to see where one is and how to best continue to the planned destination. When traveling by car one is frequently on main highways where there are lots of signs indicating the distance and direction to nearby towns. But when cycling one is more often on secondary minor roads which have far fewer directional signs.