XC Race Tire Thread

Why does Maxxis recommend Rekon Race as a rear-only tire? Yet all of the XC bikes that spec them brand new have them both front and rear. The aspen seems to roll better than the rekon race as a rear tire, is lighter, and to me, the rekon race also has more grip up front. Even the performance ratings on the Maxxis site gives a higher cornering and braking rating to the rekon race vs the aspen.