Yeah, because those gestures are more akin to keyboard shortcuts, i.e. something for power users. OS X is perfectly usable without complicated gestures. Two-finger scrolling is the most complicated thing an average user has to learn.

This same pattern continues on iOS devices. They don't ever use complicated gestures, certainly not as the only way to accomplish something. The most complicated gesture you need is pinching.

The new iOS 5 has gestures to switch apps and get home, but those are really like keyboard shortcuts since the home button is still there and offers a simpler alternative.

There is still a problem when you accidentally trigger gestures. All my friends are scared to touch my Mac because they'd trigger hot corners all the time. With 10.7, you can easily trigger gestures even on default settings. I am worried the iOS5 gestures will have the same problem.

I'm not sure if it's just me, but the 'pinch with 3 fingers and thumb' gesture seems to be practically impossible on the older macbooks with a separate pad & button - there just isn't the space.

That's completely okay because those older touchpads don't support gestures beyond two-finger-scroll anyway.

No, it supports both 3 finger swipe (fwd/back in browsers), and 4 finger swipe (change Space), as well as, iirc 3 finger touch & click (although I haven't got this working since I installed Lion)