Pai Gow Poker - why don't casinos offer "buy bets"?

In most or all California card rooms that have "corporation" banked pai gow tables, you can "buy action" on a hand, paying roughly 5% vig up front per hand, betting that the particular hand will lose against the banker hand.

Why don't casinos offer this? They allow player banking. Seems like an extra way to make more $$.