This is the correct answer.
Books make so much money off people like you they don't NEED to fix the games, it's more risk and and more work than it's worth.
Books shade lines quite often, thus accepted a minute amount of risk in exchange for a maximization of profit. Having equal action on both sides of a game guarantees zero risk, but the book can make more money by offering a worse line on the side they believe is going to win. Thus pointspreads and totals are not truly 50/50 propositions as they are purported to be, so from that perspective you could say it is 'fixed'. It's like flipping a slightly weighted coin.
The thing about conspiracy theories, though, is that they generally aren't true because a fundamental tenet of any conspiracy is that it requires a large group of people do both be smart and keep a secret for an extended period of time. People think the Bush administration was smart enough to stage 9/11, yet they couldn't figure out what was happening in New Orleans while it was on tv? Same thing goes with sports. For the fix to be in you need a TON of people to know about it: Books, players, management, and thousands of intermediaries, not to mention the people who would have to be betting 10s of millions (maybe even hundreds of millions) in order for it to even be worth fixing a game.
Not to mention that in several instances of fixed games (ie thrown boxing matches) it has been exposed, thus furthering the idea that this many people can not keep a secret for long.
There will always be people like you screaming "omg rigged!!!" every time they lose, but you're probably the same sort of person who, when they win 5 -EV bets in a row, think you're God's gift to the world and decide to go tout.
Sorry you lost your bet. After this thread, I hope you get used to it, because it will happen to you frequently based on your attitude. Good luck.