Why do Spread Betting Bookies hate Arbitrage Traders? Q. Why do spread betting bookies hate arbers? A: Simple. Spread betting providers don't like arbers (except ProSpreads, a spread betting platform designed for daytraders) because, in the long run, they always win and the bookmaking industry always loses. No company is so arrogant as to believe that the spread they make is always correct, and that they are always going to end up on the right side of a client taking advantage of arbitrage opportunities. It's a straightforward transfer of wealth from the two bookmakers involved to the arber. In the long run each bookmaker will end up wearing half the loss.