For example, I doubt many people could put their hand of their heart and claim horse-racing was entirely straight, not least because the borderline between straight and bent is actually somewhat blurred.
There are varying degrees to which someone might legitimately push a horse, it can be hard to be entirely uninfluenced by the fact that if you know part way through a race that you really aren't going to get a prize-winning place, then failing to push the horse to the utmost, and ending up somewhere behind where you might have ended up might enable the horse's owner and their friends you to get better odds in a future race.
Apart from blatant cases, it can be very hard to prove that someone wasn't trying, not least because horses can have off-days even when they actually have been perfectly prepared for a race, and no-one can easily question a horse.
To an extent, the cynical person might well assume that much dodgy stuff *might* be happening, wondering whether a particular cyclist/track athlete actually won with or without the aid of drugs, whether a particular sport was or wasn't being fixed for betting purposes, etc.
Nevertheless, on the occasions when someone actually does end up being shown to have put gain ahead of sportsmanship, that doesn't mean that even the cynical person isn't justified in looking down on the culprit, whether for confirming their worst suspicions, or just for being dumb enough to get caught.