That's not likely to change anytime soon either.
All those top Holden drivers have proven themselves over the past 10yrs.... Skaife, Tander, Kelly Brothers, they all have Championship or Bathurst/Sandown wins between them like they are going out of fashion.
Then you look at the very few top ford drivers that are still trying to prove themselves... Lowndes (in a ford), Bright, Winterbottom, Whincup. Sure they can all drive but they are still all trying to win something for themselves instead of sacrifice points/wins to let other Ford drivers/teams win.