I think one of the issues is that the officials are not full time employees. Most of them are professionals (lawyers, engineers, businessmen), and those professions leave very little time to master officiating. I'd feel a lot better if the refs were full time. Hell I'd even apply to be one if they'd agree to never let me officiate a Bills game ?
Interestingly enough, the fact that many are professionals theoretically makes them less susceptible to bribes. Corrupt judges and police are less common in places where they are paid enough to live comfortably, for example. Bribes are much more tempting when you are struggling to put food on your family's table. That's partly why corruption is so rampant in the developing world.