Because GPS isn't working. Here's the fix:
Open the Phone, as if you were going to make a phone call and dial -
*#9090# -- Diagnostic Configuration (*#197328640# if that doesn't work)
Menu, select Key Input, enter Q
Menu, select Key Input, enter 0000
wait for the next menu. (It takes a while.)
UMTS->COMMON->NV REBUILD->NV REBUILD->SYSTEM->PROTOCOL->GPS->IMS
or, if you don't have UMTS:
UE SETTINGS & INFO->SETTING->SYSTEM->NV REBUILD->ALL
Restart the phone.