Sorry, Ed. I guess that sounded a bit rude.
Oh, and Pharoah, Ed's explanation is pretty right. But just to point out WHY apple are no longer allowing us to boot into classic: by booting into classic a user can circumvent the file-system security of Mac OS X! This would require physical access to the machine, as the user would have to hard-reset the machine and probably need to boot from a CD, but it is a security hole nevertheless. By ensuring that your Mac won't boot into OS 9, Apple have made sure nobody can get access to your locked-away data even if they had access to your machine (ie: if it was stolen).
You can, apparently, still run classic in an emulation mode (though I can't imagine how you actually install classic into the system, now) which is handy for older programs and games.