Why Do We Have To Convert Our TV From Digital To Analog?

Of course it will improve picture and sound quality but why are we being forced to use a digital to analog TV converter box? In 1996 congress passed legislation mandating the change from analog to digital TV broadcasts that is now aproching the cut off date of Feburary 17, 2009. Digital transmissions make more efficient use of the broadcast spectrum so there is more room on the digital spectrum. Once analog TV broadcasts end, those frequencies are returned to the federal government to be used for communications systems for police and fire departments and other public saftey uses.