Probably because of the expense of Hornady brass. Most dealers in my area don't stock Hornady brass. Recently, I was in dire need of .308 brass, and found some Hornady .308 match brass at a dealer about 50 miles distant. It was very pricey. About a buck a piece if memory serves me. I will say though that it was the most perfect rifle brass i have ever purchased.
Every piece was the correct o.a.l., primer flash holes needed no deburring, all cases dropped into the case gage with no sizing, and case weight was very consistent. All things considered, it was the most perfectly dimensioned rifle brass i ever purchased. ....just pricey.