Sacrifice Ground Ball Rule: Why the Difference from Sac Fly/Bunt?

Question
WHY is there no "sacrifice ground ball" in the same way as the sac fly and sac bunt?   if there is going to be a batting average allowance (i.e. the sac fly and sac bunt do not count as an at-bat) for a "sac fly" that scores a run,  why is there not a provision for a ground ball that accomplishes the same thing??  the rbi in those instances where the grounder scores the run is awarded...why is the AB not waived as it is with a sac fly?

Answer
Mitch,

That's the rulebook!  If I was guessing, I'd say the reason a ground ball isn't a sacrifice is because the batter is trying for a hit.  A sacrifice was meant as a way you give yourself up, and that really only happens on a bunt.  In fact, the real question should be why is a sacrifice fly a sacrifice?  They just happen to be lucky enough to hit a fly ball when someone is on third.

Brian