@bythewell - It's still gambling, no matter what they think. They might be making their odds a little bit better, but not by much I'd wager.
If you could really predict what would happen, people would win more often. There are a lot of smart people in the world and there's a lot of money in horse racing. If you were willing to dedicate a lot of time to researching it, you could make a lot of money.
Of course, there might be people who do that. There are professional poker players and slot jockeys after all.
The horse racing handicap system must just make it more difficult for them to win, since if you've got a sure thing with low odds, you're better off playing that I imagine and it's difficult to get sure odds if they have been balanced by the house as closely as possible.