Apple's obsession with a one-button mouse dates all the way back to the 1983 release of the Lisa, the company's first PC to ship with a mouse.
According to Walter Isaacson's biography of Steve Jobs, the late Apple co-founder insisted on a one-button mouse for simplicity's sake. The three-button mouse Apple saw Xerox demonstrate was too busy and confusing, Jobs argued.
Apple eventually came around on right-clicking ... sort of. Apple first enabled users to CTRL-click to simulate a right click. It then began to support right-click mice with the 1997 release of Mac OS 8. And with the 2005 introduction of the "Mighty Mouse," Apple finally made a mouse with a programmable button that could be used for right clicking.
By default, Apple mice still don't have right-click enabled, though.
