Re: At last...
Go back a few years in time to Mac OS X 10.4 (Tiger). It had initial support for 64-bit apps. Most apps, including system services, were 32-bit though.
It took them another version, 10.5 (Leopard), to implement 64-bit system apps ...
... and another version to fully go 64-bit, going almost fully 64-bit system apps with 10.6 (Snow Leopard) and only running on x64-capable CPUs. And even then some other apps still ran 32-bit (iTunes/Front Row/...)
Edit: And 32-bit apps are still supported to this day, only to be dropped soon.
TL;DR: Transitions don't happen all at once lest people rage.
Biting the hand that feeds IT
