riddle me this....

Mountain bikes are very much classified on HTA, XC race bikes typicly have a HTA of 70 - 72 degrees, whil my cannondale has a HTA of 69 degrees. My hard tail is in the 71 degree range and is noticably twitchier and also more nimble. this may also be atributed to weight and bike length, the cannondale is looonnngggg.

so , why is the given HTA for a " race geometry " so steep? is there any associated climbing benefits to a steep HTA?