There were lots of events happened in 60's. In particular, Vietnam War and Space Race had a huge influence on people, culture and technology development at that time. People was dreaming new technology, so 60's is the dawn of the new technology age.
It was the same time that musicians began to use electric sounds. Following this, the first synthesizer was made in 1965 against the background of that electric parts as surplus were cheap by Vietnam War. The synthesizer reminds people of hardware rather than software. However desktop interface is always based on hardware. Windows 67 was designed by using it as metaphor.