First of all it’s a very difficult job. Action happens super fast and quick decisions are difficult. Sometimes if you’re playing a sport, it is easier to feel the foul, or you know if you were safe or not. But when you’re only watching the action, and not actually in the play, it can be difficult to judge.
The massive television coverage and instant replay has brought more pressure and scrutiny upon officials. Hometown crowd pressure has to at least have some play in it. Like athletes who make mistakes and errors, the refs and umps do also. It’s part of the game and you have to accept it and move on. There are cases where people will be extorted or blackmailed.
There is the stereotype of debtors getting beat-up or thrown into the river if they don’t pay up. The anti-gambling establishment will point to bankruptcy and corruption as reasons to stamp out illegal gambling. Politically it can’t hurt the cops, D.A., etc. to bust a gambling ring prior to an election. It won’t be beneath the cops to bust even the smallest of small time players. These are the easiest people for the cops to get, which will lead them to bigger fish to fry. Although society puts a low priority on it, it is best not to sports gamble illegally.