I think a lot of that has to do with premium sale numbers, breed divisions, and how Texas majors take X number of steers from each class in the premium sales. It encourages a diversity of breeds (at those shows that split breeds) - I know sheer numbers are much greater in Texas, but if you compared percentages, I think you'd find that Texas will have a higher percentage of Charolais, all the British breeds, and American breeds than pretty much anyplace else.
At OYE this year, only 3 steers from the Charolais division were eligible for the premium sale. A few Charolais steers show in the crossbred division, an occasional one or two in the Chi's, but that's not a lot of encouragement for most folks to want to feed one. It's all on percentages (if 5% of the steers in the show are Charolais, then 5% of the steers in the sale are Charolais - if 30% of the steers in the show are crossbreds, then 30% of the steers in the sale will be crosses) but most people prefer the chance of getting in as 1 of 18 crosses or 1 of 8 Chi's to the shot of being 1 of 3 Charolais chosen...
And here in Oklahoma, there's still the perception that it takes a black one to win - usually that holds true. Not many folks here are willing to spend what it usually takes to buy a Charolais cross prospect that looks like he might be capable of winning it all one day - if they're going to spend big money on one for OYE or Tulsa, it's most likely gonna be a black one.