Ogres and Hill giants are both of Giant type and are described as very similar height: 9–10 feet for ogres, 10½ feet for hill giants (and they're both of Large size category). Yet their described weight is vastly different (600–650 lbs. vs. 1100 lbs.), as are their abilities.
The ogre is a CR 3 monster with 4 HD and a strength of 21.
The hill giant has CR 7, 12 HD and strength 25.
Where does this difference come from? Is there a fluff justification for it? Or has there ever been any official explanation of why the hill giant (and other giants) was made much shorter than its 2nd-edition incarnation (which was 16'), while most of its abilities seem to have stayed?