Why can't I buy Scott heat-resistant bluegrass seeds in a bag alone?

Question:Scott sells seed mixtures such as Thermal Blue and Reseed Supreme which have 9% to 14% bluegrass, and the rest tall fescue. The bluegrass is their own variety developed to be resistant to heat and drought. But they don't seem to sell any of that bluegrass variety as a bag of seeds. Just in mixtures.

Are they trying to hide something? Does that bluegrass have obvious defects which are concealed by the tall fescue? Or what?

Answers:
Maybe it's too hard for them to sell it at a profit if it's 100% bluegrass.