Geno was quoted on this topic years ago and posed the question back (if memory serves) on why more ADs weren't demanding better results, beyond the wins and losses.
I suspect many AD's are too unadventuresome to pay much attention to wcbb so they just take the easy route. Like the lazy Director of Information Technology who made the safe choice and bought IBM in the 1950's and '60's, when every other computer company offered more powerful systems for less money.
Safe choices.