Need for extended cubic-beziers

Hey all,

So in my travels around the web animation community, I've noticed more than
one lamentation that the cubic-bezier timing function doesn't take more
than two coordinates, leaving bounces and other such animations woefully
beyond the reach of most CSS animators.

Such bounces are a much-touted feature of JS animation libraries like
GreenSock and were easily available in Flash back in the day.

I'm new here, so I don't know if this has been discussed before. Is there a
reason *not* to support advanced curves?