I occasionally wonder why Mac/ia32 existed as well.
My conclusion has been that when Mac’s first switched to intel there was a combo problem - intel’s mobile chips were still mostly 32bit (remember intel dropped the ball on 64bit), and more importantly while ppc mac’s were capable of 64bit (the G5 cheese grater) the majority of the desktop was iffy, coupled with things like flash, etc that were 32bit.
My conclusion has been that when Mac’s first switched to intel there was a combo problem - intel’s mobile chips were still mostly 32bit (remember intel dropped the ball on 64bit), and more importantly while ppc mac’s were capable of 64bit (the G5 cheese grater) the majority of the desktop was iffy, coupled with things like flash, etc that were 32bit.