Soy vs estoy

Question

If estar is to be used with a location, why use ser to discuss where one is from?

Answer

Hola Greg
The second context (where you are from) is not so much about where something/someone is located; it is referring to the "origin" (in this case it is ser):
Estoy en Madrid (I am [located] in Madrid) 
This one says where the person is physically. 
Soy de Madrid (I am [originally] from Madrid) 
This one doesn't say where the person is physically, but where he/she comes from.
Un saludo
Inma

Answer

Because ser is to be in a situation that does not change. You will be for ever from your birthtown. But  estar is to be in a situation that does change. Today you are in Madrid, tomorrow you are in New York.