The problem is, we don't know which matches are fixed or not. Usually we (as bettors) will feel it as the game goes on.
Big league matches are not always available, usually the big league matches will take place on weekends. If you are a football matches bettor, you should know what to do when you really want to bet on a football match. That's the reason why bettors will bet on football matches even in the lower class leagues.
Almost everything you will do has risks, including gambling. And talking about the possibility of winning in football, I think it will always be 50:50. It depends on how you deal with the match situation.