It's easy to understand the disparity in system requirements.
Adobe's goal is to sell software to the widest market they can afford to develop and test for. They can't afford to make Lightroom work on every Mac made in the last 10 years, but they can make it work on a lot of them.
Apple's goal is to sell Macs (and, OK, iPods). Aperture and Motion are designed not only to sell applications and showcase the Mac, and their system requirements are cleverly narrowed enough that if they induce the intended amount of lust in us, well, we all need to go out and buy new hardware.
Adobe is happy if you simply buy their application. In comparison, it was probably never Apple's intention to let you go with just the application. Apple's pricing plan is, if you're rich enough to drop $500 on a 1.0 version of a niche photo or video product, you just qualified yourself as a legitimate sales prospect for the other $10000 of hardware. The system requirements serve that goal.