The long runways appear to be for "hot and high" operations or at aircraft test facilities.
I asked a well connected friend a while ago about Shuttle landing sites and he passed on the request to colleagues in NASA. I cannot verify the accuracy but the reply was:
"There are TAL (Trans-oceanic Abort Landing) sites in Northern Africa and Spain. They are in place in case one or more Shuttle main engines fail during the first few minutes of the 8 1/2 minute climb to orbit. The two main TAL sites in Africa are Banjul in the Gambia and Ben Guerir in Morocco.
The TAL sites in Africa are used for low inclination orbits while sites in Spain support higher inclination orbits. Since all future Shuttle missions are to the ISS which is a 51.6 degree inclination orbit, only sites in Spain will see any TAL support requirements in the future.
[This was written before Columbia was lost.] The
two main sites in Spain are Moron and Zaragosa.
. . .the TAL abort options disappear at about 5 1/2 minutes into the launch when AOA (Abort Once Around) and ATO (Abort To Orbit) become the prime options if a SSME
[main engine] fails."
This info seems to be backed up on this site:
http://www-pao.ksc.nasa.gov/kscpao/nasafact/tal.htm