And why only athletes?
Seems like they only asked for the geolocation data specific to the athletic training facility. Low hanging fruit. Only athletes and support staff would be in those buildings.
If they asked for data from the whole city of Ames, you might get some low-hanging fruit (like if the account was registered to an 85 year old from Alabama), but - more likely there would be so much data it would be overwhelming. This is just me speculating, I have no inside knowledge.