Andru offers some theory as to why Apple has not shipped Macs with a two button mouse yet. Makes sense to me. One argument he uses is that most novice computer users are not even aware that there are functions applied to the right mouse button.

How many times have you been talking your mom or grandmother through a task on their PC and said “Right-click on this.” The usual response is “right what?”.

One of the other reasons is that Apple wants developers to follow their interface guidelines.