You're right, any reputable gambling sport should not engage on match fixing in other for them to gain their spectators trust, those that do this at the local level may not be that observant about it to that extent by knowing if the people really want that or not, but i see no gain in fixing a match than where manipulations is an order of the day, people may not want to for such sports to gamble because they know that it's been fixed by the organizers.
Let me correct you, match fixing had nothing to do with the spectators, its all about making more money at a little space of time, the bigger boys meets with the clubs leaders of little clubs and offers them good money that they only dream of making, being poor, they oblige and fix the matches to their sponsors advantage, the match plays and these big gamblers smash the bookies and make huge compensation for themselves, the club owners and those involved also makes it big too from the bookies and they're satisfied. The spectators of such teams aren't that much influential people that can raise dust, that's why they don't bother about them while fixing matches. Their key aim is to make a lot of money.