The books rarely balance up though, especially for markets with more than two outcomes. Football/soccer has win/lose/draw (and you can never get enough money on the draw, as hardly any amateur is going be watching a match cheering on a draw!)
Horse racing is even worse for the bookies, with multiple runners, their books will rarely balance, and the standard outcome is a loss if the favourite wins. Any outsider winning a race is a ‘turn up for the books’. (n.b. this is for UK style horse racing betting, where the bookies offer fixed odds. Pari-mutuel or pool betting doesn’t have the same problem)
Horse racing is even worse for the bookies, with multiple runners, their books will rarely balance, and the standard outcome is a loss if the favourite wins. Any outsider winning a race is a ‘turn up for the books’. (n.b. this is for UK style horse racing betting, where the bookies offer fixed odds. Pari-mutuel or pool betting doesn’t have the same problem)