[quote name='skej21' timestamp='1328265011' post='1524535']
Surely if your technique is good enough, two should suffice?
[/quote]
Of course that's right. However, there is always the case for developing your playing style. Keeps everything fresh. And of course you can keep everything fresh using different styles playing with two fingers. Whatever suits the individual. Gary Willis' explanation is quite simple. He started playing with three fingers so he's never known any different.