In Streaming API, I wonder why coordinates, place, and geo values are all "none" although location parameter is set in mostly result? So how does the API know that the results are associated to that location?
Coordinates, place and geo are all characteristics of a Tweet. It depends on whether or not the user activated location services on his device. However, location is a characteristic of a user. It was first set when the user created his account. That's why you're seeing it in most results. According to the description in Twitter's Documentation,
Nullable. The user-defined location for this account's profile. Not necessarily a location nor parseable. This field will occasionally be fuzzily interpreted by the Search service.
Example:
"location":"San Francisco, CA"