Hmmm.. well I think the most obvious is just conviene, say you were meeting up with a friend and he/she was trying to explain where he/she was but it was too confusing, it would be super convenient if he/she just sent you her/his location via and app or something and you could find them much easier.
Another reason would be safety, my aunt gave her son a smart watch that has a gps tracker in it so if he was ever lost she could always see where he was with her app. I think that gps trackers are most useful for safeteness.
And sorry but that's all I could think of I'll keep thinking and if I think of anything else I'll let you know. ☺️