There could be many reasons for a station not to be interested, several of which have been stated already. You are asking them to sell something they created wearing their “journalist” hats. This could well compromise their standing as journalists. After all, they don’t know, or can’t be assured, of what you will do with the footage.
It is probably harder to use footage in a cooperative fashion than if you were openly antagonistic. For example, The Colbert Report and The Daily Show use news coverage all the time (I assume without permission). You may want to investigate the concept of “Fair Use”.
Bob C
(“I AM NOT A LAWYER.”)