Maybe the downloadables are honest.... Never played BJ that way.

How others play is not the point. Point is that site owners want more of a "sure thing" than the measly .4% they will grind out against perfect basic strategy players. Their primary business is not BJ, and they don't want to get clobbered (which they sometimes would if they offered an honest game at high stakes). They're apparently not worried about losing customers as they only offer it as a 'side light' anyway. The rigged program protects them well and also increases their profitability. Also makes it less of a certainty that you actually are +EV even with the bonus...