It also infects players and referees. It's harder to trust referees in a sport where you know what the big bets are, whether or not the refs are actually cheating to try to change the outcome it's hard not to feel that they might be.
Baseball alone has had some prominent sports gambling by players in its past change the record books. There's a bunch of interesting arguments for and against that maybe the records for Joe Jackson and Pete Rose should be reinstated now that sports gambling is so generally legal in so many more states than their time. There's a bunch of interesting arguments of how many of today's players might be "on the take" as much as or worse than those historic gambling scandals.
Other sports have their own histories with it. Sports are different when you are wondering if even players are betting for or against themselves.
Isn't there rules about anyone in a sport (players, managers, referees...) not being allowed to bet? I work with people who are not allowed to trade commodities because they are in a division where people who make those commodities store data that isn't yet public knowledge. The SEC knows who those people are and the list is sent to every broker to ensure they can't trade.
If sports betting isn't checking on this and cracking down there is a major problem.