Why is Flash so hard on the CPU?

Question

Recently I hear Steve Jobs citing this as a main reason to not have Flash on IPADS

Answer 1

If you look at processor utilization of Flash, it's significantly higher on the mac than the PC. The next release of the flash player (10.1) will make it much better, but not the same as the PC.

I read somewhere that part of the reason is the video. On Windows, applications have access to hardware acceleration to speed things along, on OS X, the necessary API's aren't available for flash to use. Also, flash can't easily utilize multiple processors so it's limited in that sense too.