Going only by what I recall having read over the years, cast aftermarket roller cams got either a bad rep -- or a bum rap -- for durability issues with the higher-than-stock spring loads performance cams generally require. They were less expensive and didn't require anything special for a distributor gear, but people tried to use them in applications that really needed billet cores and had problems.

They were (are?) common for SBC and SBF; may have been available for some SBMs, too. I don't remember any cast roller cores for BBM.