I think a more appropriate question would be "Why wouldn’t your organization be thinking about it?".
Having worked with organizations providing services into the Government, we were mandated (as part of our contract of service) to conform to ISO20000.
It would therefore seem essential for any organization either delivering service into the Public Sector, or with significant Public Sector links to look towards ISO20000 at the earliest opportunity, before the inevitable is forced upon them.
From experience I have found that the benefits in going through the pains of introducing ISO20000 are well worth it.