if i understand it correctly, the ability to make a 50/50 bet of your spin win (multiple times, no less) and have it count toward your wagering requirement made these bonuses +EV. i think most, if not all, of the casinos stopped counting the bets toward the WR, so they became -EV propositions. that's why they were removed from the original casino post.
for those who know more details (ED?), please correct me if i'm wrong on this.